Arachnida

(Spiders, scorpions, mites, and ticks)

Phylum Arthropida

Class Chelicerata

Subclass Arachnida

Number of families 648

Thumbnail description
Highly recognizable and populous eight-legged invertebrates with two body parts (a prosoma and an abdomen), pedipalps, book lungs or tracheae, sometimes poisonous fangs, and generally the ability to produce silk; they are terrestrial chelicerates (invertebrates with pincershaped mouthparts)

Evolution and systematics

Fossil records suggest that arachnids were among the first animals to live on land, switching from water- to air-breathing. The oldest known arachnid fossils date from the Silurian Period, more than 417 million years ago. It is during this period of time that scorpions (order Scorpionida) appear to have left the water for life on land. Many paleontology experts presume that scorpions were the first animals to make the transition from water to land. In fact, the histological resemblance between the gills of king crabs and the lungs of scorpions help to support this hypothesis. However, the subphylum Cheliceraformes, as a whole, spent many millions of years in the water before it became terrestrial. More than 60,000 species of arachnids are described, although many species, especially mites, remain undiscovered or discoveredbut-not-yet-described. Spiders, mites, and ticks constitute the largest and most diverse orders of arachnids. Among the extant species, scorpions are known to have had a long maritime history that continued well after some of them switched to living on land. The marine-living scorpions, at that time, were very large, some up to 3.3 ft (1 m) in length. The harvestmen (daddy longlegs) are also believed to have had a pre-terrestrial history in the sea.

Currently, arachnids constitute the subclass Arachnida, in the phylum Arthropoda. The subclass is divided into 11 distinct orders: Acari (mites, chiggers, and ticks), Amblypygi (tailless whip scorpions), Araneae (spiders), Opiliones (daddy longlegs), Palpigradi (palpigrades), Pseudoscorpiones (false scorpions), Ricinulei (ricinuleids), Schizomida (micro whip scorpions or schizomids), Scorpionida (scorpions), Solpugida (wind scorpions or solifugids), and Uropygi (whip scorpions and vinegaroons). Many scientists now categorize Arachnida at the class level.

Physical characteristics

There are at least 10 features of arachnids that are often used to describe the group, including:

• carapace may be uniform or in part segmented
• pedicel may be absent or present
• sternum may be uniform or segmented
• opisthosoma may be uniform or segmented
• chelicerae may contain two or three segments (podomeres)
• pedipalpi may be pincer-like or leg-like
• coxae of legs or pedipalpi may or may not contain gnathobases (plate-like anterior expansions)
• first leg may be used as a leg or like an antenna
• legs may be of seven segments (podomeres) or may be sub-segmented anywhere

• coxae may meet and hide the sternum or may be separated

Anatomical features such as two pairs of limbs, the pedipalps and chelicerae, are distinctively present but greatly modified for different uses in various arachnid species.

The 18-segment arachnid body is often protected by sternites below and tergites above, connected by a soft pleural membrane, and is divided into two tagmata: anterior and posterior. The anterior (front) part, called the cephalothorax (or prosoma), contains sense organs, mouthparts, and limbs or appendages in pairs. The cephalothorax is composed of an anterior, unsegmented region called the acron, and six true segments (each bearing a pair of appendages). It accommodates both the head and limbs. A carapace-like shield completely or partially covers the cephalothorax of arachnids. The first pair of limbs (chelicerae) attached in front of the mouth may form pincers or poison fangs, and the second pair (pedipalps) behind the chelicerae may serve as pincers, feelers, or additional legs. The other limb pairs are used for walking. The 12-segment posterior (rear) part of the body, the abdomen (or opisthosoma), contains the genital opening and other structures. The abdomen may be segmented (as in scorpions) or unsegmented (as in most ticks and spiders). Abdominal appendages are either lacking, or modified into special organs such as the spinnerets of spiders and the pectines of scorpions.

Arachnids breathe by means of tracheae (windpipes), book lungs (modified gills), or both. The mouth of arachnids is not readily noticeable from the external surface. They do not possess jaws (mandibles), but instead have cutting or piercing appendages called chelicerae. The open circulatory system distributes blood from the heart to an enlarged blood space by the use of arteries. The heart is a tubular organ located dorsal to the mid-gut, containing various openings so that blood can be returned to the heart. The central nervous system consists of two cerebral ganglia connected to a pair of sub-esophageal ganglia by means of a circum-esophageal linkage (commisure). Arachnids possess a number of sense organs, many related with the outer body covering (cuticle). The most common of these sense organs is the hair-like setae that are sensitive to various stimuli; they are generally located throughout the surface of the body.

Distribution

Arachnids are found throughout the world from equatorial to polar regions, but reach their most abundant numbers and diversities in very warm to hot, arid and tropical/subtropical regions.

Habitat

Arachnids are essentially terrestrial animals that are found in nearly every habitat around the world.

Behavior

Arachnids are terrestrial, except for some mites and a few spiders that can still be found in water. Most arachnids are solitary creatures, other than during mating periods. Even normally sedentary species will roam when in search of a mate. A courtship ritual usually precedes reproduction. A large proportion of their lives are spent in long periods of inactivity, often waiting for prey to stumble upon them. When disturbed by possible danger, they often fall motionless, acting dead, and try to appear nearly invisible to approaching enemies. Regular activities are instinctive by nature, geared primarily toward perpetuating the particular species and activated by external circumstances (such as the general environment and light intensity) and internal adaptations that have been modifying over thousands of years. Some species ambush their prey, while others chase them down. They feed on specialized prey or on many different types of food, depending on species. Arachnids also feed in various ways: as herbivores, scavengers, parasites, cannibals, and carnivores.

Feeding ecology and diet

Arachnids are predaceous, either actively hunting or patiently lying in wait for small animals such as insects. They have various structures that are geared to capturing prey. Some of these features are the segmented, stinging tail of scorpions and the abdominal spinnerets (that allow for the construction of insect traps, or webs) of spiders. Since they do not have the ability to masticate (chew) their food with their mouthparts, they are generally able only to feed on the fluids of their prey. After piercing the prey's body wall with their chelicerae, arachnids will either ingest the fluid contents or digest the tissues externally with enzyme-containing secretions that are ejected from the mid-gut (as with spiders) or the salivary glands (as with ticks and mites). A powerful suctorial pharynx draws the fluid up through the pre-oral food canal and delivers it into the mid-gut. Gaseous exchange occurs in a variety of ways. Respiratory gases may enter and leave the body through specialized structures (either lungbooks or spiracles) or may diffuse through the cuticle (as in some mites and larval ticks).

Reproductive biology

During mating, a variety of complex behavior patterns are normally observed. Generally, the reproductive organs are

contained in the abdomen and open ventrally on the second abdominal somite. Male sex organs may consist of one diffuse testis or one or two compact testes. The spermatozoa produced are conveyed to a median gonopore through one or two excretory ducts (vasa deferentia). Insemination into the female may come from the male gonopore in a liquid medium (as in spiders) or may be contained in packages called spermatophores (as in ticks and scorpions). An intermittent organ or penis may or may not be present to direct the spermatozoa into the female during mating. Females possess a single or paired ovary, which may be either compact or diffuse and one or two oviducts may lead to the median gonopore. Eggs may be laid underground, in the shelter of a stone, under tree bark, enclosed in a cocoon, or other variations of these methods and structures. Females usually guard eggs or young, which are often born live and as miniatures of the adult with regard to appearance. Eggs may number from one to more than 1,000 in a single brood.

Conservation status

As a group, arachnids are considered abundant all over the world. Some species are diminished in numbers, even considered rare or endangered, because of internal circumstances (such as limitations of habitat) or external circumstances (such as human activities). The 2002 IUCN Red List includes 18 arachnid species: one as Endangered; nine as Vulnerable; one as Lower Risk/Near Threatened; and seven as Data Deficient.

Significance to humans

Most arachnids are harmless and contribute to the give and take of nature by controlling the populations of the insects they prey on or the plants, reptiles, birds, or mammals that serve as their hosts. A few species are serious agricultural pests. The bites of some spiders, such as the black widow spider and the brown recluse spider, and the stings of a few species of scorpions are dangerously poisonous to humans.

Species accounts

List of Species

Demodicid

Demodex folliculorum

order

Acari

family

Demodicidae

taxonomy

Demodex folliculorum Berger, 1841.

other common names

English: Face mite, hair follicle mite.

physical characteristics

Microscopic, elongated parasitic mite that is 0.00394–0.0178 in (0.1–0.4 mm) in length; worm-like appearance, with distinct head-neck part and body-tail part; long, tapering annulated abdomen. Adults possess four pairs of short legs (basically stumps) on head-neck part; legs contain tiny, but strong claws. Body is mostly semi-transparent. Needle-like mouthparts are used for eating skin cells; it is covered by cuticle surface that shows numerous striations. Bodies are layered with scales, which keeps them secured to follicles of hosts. Does not have excretory opening because its digestive system produces very little waste. Peritremes are absent, and palps (pedipalpi) are reduced in number and size.

distribution

Worldwide.

habitat

Lives in hair follicles of humans; primarily on pores of facial skin and sebaceous glands of forehead, nose, and chin; often in roots of eyelashes. However, it may inhabit follicles, with or without hair, anywhere on body. More common on humans with oily skin or those who use excessive amounts of cosmetics and fail to cleanse skin properly.

behavior

Lives in hair follicles and eyelashes with heads buried first into root. Migrates onto skin during nighttime at rate of 0.4 in (1 cm) per hour.

feeding ecology and diet

Parasitic, eating skin cells of humans.

reproductive biology

Females may lay up to 20–25 oval eggs on one hair follicle. Larvae (protonymph) and nymphs (deutonymph), with physical features similar to adults, are swept by sebaceous flow to mouth of follicle. First stage larvae emerge without legs. Larvae in later stages have six legs, as opposed to eight for adults. As immature mites grow, they become tightly packed. When mature, mites leave follicle, mate, and find new follicle in which to lay eggs. Entire life cycle spent on host: 14–18 days.

conservation status

Not listed by the IUCN.

significance to humans

Acute and chronic inflammation and infection often result when large numbers congregate in single follicle. If too many mites are buried in same follicle, the eyelash may fall out. It is basically harmless and is not known to transmit diseases, but large numbers may cause itching and skin disorders, referred to as demodicosis. The incidence of demodicosis occurs worldwide, being more prevalent in older humans. When humans are infested, they may show no symptoms.

Rocky Mountain wood tick

Dermacentor andersoni

order

Acari

family

Ixodidae

taxonomy

Dermacentor andersoni Stiles, 1908.

other common names

English: Paralysis tick, Rocky Mountain spotted fever tick.

physical characteristics

Includes a large collection of diverse types of mites, chiggers, and ticks; carries parasites and disease; has adult length of 0.08–0.65 in (2.1–16.5 mm). Specifically, unengorged females have length of 0.11–0.21 in (2.8–5.4 mm), adult males a length

of 0.08–0.24 in (2.1–6.1 mm), and engorged females a length of up to 0.65 in (16.5 mm) and a width of up to 0.45 in (11.4 mm). The body, covered with hard protective covering, is pear shaped, and is dorsoventrally flattened (top to bottom). Immature instars and adult females possess a strong pro-dorsal scle-rite, with the opisthosoma being covered with soft cuticle to permit engorgement. Holodorsal shield is found on adult males; posterior idiosoma is flattened, anterior gnathosoma is articulated. Tectum is well developed. Coxal glands are absent, and water control is performed through salivary glands.

Color of adult females is reddish brown with grayish white dorsal shield (scutum) near front of body, which changes to grayish color when engorged; adult males are spotted with brown and gray, and do not have distinctive white shield; they possess simple eyes, located on the margin of scutum. Capitulum is apparent from above; basis capitulum is rectangular in shape with sides not laterally produced and approximately length of mouthparts. There are 11 abdominal festoons. Anal groove is located posterior to anus. Broad spiracular plates, located on underside of body, possess blunt process that usually reaches dorsum; goblets, located within spiracular plates, are moderate in size and number.

distribution

Widely distributed in North America, primarily throughout Rocky Mountain states and into southwestern Canada. Specific areas are central British Columbia through southern Alberta into southwestern Saskatchewan; south through eastern Washington, Oregon, and California; all of Montana, Idaho, Wyoming, Nevada, and Arizona; western Oklahoma to northern New Mexico and Texas.

habitat

Mostly woods and meadows; those arid, brushy areas that provide food and protection for its usual hosts such as livestock, wild mammals, and humans. Over-winters in ground debris.

behavior

Usually attached to its host, but when without host it will hide in cracks and crevices or in soil. If without a host at the beginning of winter, it will over-winter under groundcover to resume seeking host in spring. It will also stop looking for hosts during hottest summer months. Generally, adults will climb to top of grasses and low shrubs to attach to hosts that brush against them. Host attachment is accomplished by secreting cement-like substance around mouthparts and inserting it into host.

feeding ecology and diet

Adults generally feed for less than one hour at a time; parasitic, feeding primarily off of terrestrial birds, reptiles, and mammals and typically feeding only from late February until mid-July. All three stages (larva, nymph, and adult) can survive for more than one year without feeding. Engorged larvae, nymphs, and unfed adults normally spend cold months in grasses and leaf litter. Larvae feed throughout the summer, with nymphs continuing possibly to late summer. Males feed for about five days without engorging, become sexually mature and ready to mate, and then will resume feeding. Females feed for up to seven days (until fully engorged), during which time they mate. Fully engorged female will increase body weight from about 0.000176 oz (5 mg) to more than 0.0247 oz (700 mg). Each stage feeds on a unique host individual. Larvae, nymphs, and adults climb grass stems and bushes while searching for host. Can detect the presence of chemicals such as carbon dioxide associated with mammals, which indicates animal's presence.

reproductive biology

Semelparous (reproduces once during lifetime, after which it dies). Requires blood meal before developing into its next life stage and for egg development. Mating takes place primarily on host, with female usually on top of male. Males do not become engorged. After feeding for 4–17 days, mated female descends from host and seeks protected area to lay eggs. In spring, after a preoviposition period of usually 3–11 days, she lays single cluster of usually 3,000–5,500 (but possibly 2,500–7,400) yellowish brown ellipsoidal eggs over period of 10–33 days. Female then dies within 1–14 days. During next 7–38 days, eggs hatch if temperature is 72–90°F (22–32°C).

Young six-legged larvae begin crawling in search for small rodent host (such as mice, voles, and chipmunks), dying within 30 days if unsuccessful. Unengorged first instar larva is about 0.0236 in (0.6 mm) in length. Usually feeds for 2–8 days (usually three) to engorgement, and then drops to ground to molt within 6–21 days. May survive for more than 300 days if unfed during this time. After finding suitable small- to medium-sized host (such as rabbits, ground squirrels, marmots, and skunks), nymphs reach engorgement in 3–11 days. Second instar eight-legged nymphs are 0.0551–0.0591 in (1.4–1.5 mm) in length. After completing engorgement, they drop off again and molt into adults usually in 14–15 days (possibly in 12–120 days). Adults can survive more than a year (usually about 600 days) unfed, but after finding a suitable medium- to large-sized host (such as dogs, deer, and humans), they mate on host after partial feeding. Life cycle is 1–3 years (typically 20 months), depending primarily on host availability and various environmental stresses and conditions.

conservation status

Not listed by the IUCN.

significance to humans

Females may carry and transmit several diseases to humans, including Rocky Mountain spotted fever, tularemia, and Colorado tick fever in the United States, with only rare occurrences in Canada.

No common name

Phrynus parvulus

order

Amblypygi

family

Tarantulidae (= Phrynidae)

taxonomy

Phrynus parvulus Pocock, 1902.

other common names

None known.

physical characteristics

Whip spiders or tailless whip scorpions; a typical individual grows to 1.2 in (3 cm) in length, and does not have spinnerets or poison (venom) glands. Possesses one spine in between two longer spines on dorsal surface of pedipalpal tibia. Pedipalpi (palps) take on basket-like shape for capturing prey. Young usually have reddish palps with banded legs, while adults are colored more uniformly. First pair of elongated, whip-like legs has evolved from walking appendages to sensory defensive/tactical appendages. Antenniform first legs are covered with multiporous hairs used as olfactory sensilla. Legs lack pulvilli on

tips. Prosoma is wider than long, and covered by carapace. Opisthosoma is segmented and lacks telson and defensive glands. Prosoma and opisthosoma are connected by narrow pedical. Chelicera has basal article and fangs that are spider-like. Pedipalpal coxal endites are not fused, while raptorial distal articles possess strong spines and fold against spiny femur. There is a labium. Abdominal ganglia are moved to prosoma and fused with subesophageal ganglion. There is a pumping pharynx and a pumping stomach, and two pairs of book lungs.

distribution

Belize, Guatemala, and Costa Rica.

habitat

Found in cracks and crevices between rocks; under loose bark, logs, and litter; sometimes in caves, usually in forest environments. Humid tropics and subtropics are usually preferred locations.

behavior

Nocturnal; during day, it generally lives in wide variety of places that are usually associated with base of tree trunks. Some places can be within buttressing near tree bases, deep in crevices on trunks, in burrows (dug by other animals) or other holes at base of large trunks, and sometimes behind bark. Typically, only one animal resides in a crevice; however, one male and one female may live together. One tree trunk may house many individuals. Males change resting location more often than females; it is assumed that females may be more sedentary and males may wander more in search of mates; moves with a sideways motion. Generally solitary, but majority of interactions occurs between two aggressive males or between males and females residing in same crevice or home spot. Rather docile creature that is easily frightened. When responding to threat, will use speed for escape, rarely remaining to fight enemy. If necessary, it will use palps for pinching when disturbed or under attack by enemies.

feeding ecology and diet

Predatory, eating such small creatures as crickets, moths, and millipedes. Generally avoids eating scorpions, centipedes, large ctenids (wandering spiders), and almost all ants. Usually begins to feed at dusk, not moving very far from home, and returning at dawn. Often sits quietly on vertical trunks of trees waiting for insects to pass by. Pedipalps are used for capturing prey.

reproductive biology

Males often perform a ritualized posture when females are not present; involves opening one palp, and raising and holding bodies in air. When females are present, mating males engage in combat with other males by locking their chelicerae and palps together to fight, sometimes for periods of over one hour. Males who are accepted by females will deposit spermatophore after courting and then guide female to it. Apparently has a continuous breeding season, with females being observed with eggs throughout year. Once mated, females may wait a few months before laying eggs. Once laid, eggs number 20–40. Two to three broods occur each year. Female carries eggs underneath abdomen for 3.0–3.5 months. After hatching, young (prenymphs) crawl onto mother's back (abdomen) and stay there for 6–8 days; then they molt and leave. Young will molt 5–8 times in first year before reaching maturity. Thereafter, molting occurs 1–2 times each year, and growth continues throughout life, which often lasts many years.

conservation status

Not listed by the IUCN.

significance to humans

It is quite harmless to humans, not even possessing any poison (venom) glands.

Purse web spider

Atypus affinis

order

Araneae

family

Atypidae

taxonomy

Atypus affinis Eichwald, 1830.

other common names

English: Trap-door spider.

physical characteristics

Has a poisonous bite, is skilled in silk manufacturing, is highly intelligent and adaptive, and is significant as insect predator; has large jaw. Length is 0.28–0.59 in (7–15 mm), with female length of 0.39–0.59 in (10–15 mm) and male length of 0.28–0.35 in (7–9 mm). Adults have glossy olive-gray legs and a reddish brown abdomen; massive abdomens, with short legs and pickaxe-type fangs. Has three tarsal claws, and no claw tufts. Possesses pedipalpal coxae, with well-developed endites (median lobes). Labium is fused with sternum, eyes are closely grouped, and there are six spinnerets.

distribution

Northwest Europe, especially England.

habitat

Lives in temperate grasslands, shrub-lands, meadows, and pastures, often in sandy or chalky areas. Usually found in densely woven, silken tubes (or "purses") sealed at both ends. The subterranean tubes, about 10 in (25 cm) long and thickness of small finger, are used as shelter and as tool to capture prey. Main part of tube is in the ground about 5.9–7.9 in (15–20 cm) in length, but it can reach up to about 20 in (50 cm). Part that sticks up above the surface is usually about 2 in (5 cm) in length, and normally located near a tree trunk. Tubes are well camouflaged with sand and various debris.

behavior

Digs hole in ground, up to 19.7 in (50 cm) deep, and lines it with silk. Aboveground, tube extends for several inches (centimeters). Tube is covered with sand and debris, which makes it difficult for predators to see, but easy for spider to capture prey. Often lies at bottom of tube, folded up in a compact shape. Because it hides so deep in ground, it is difficult to find. It is fearful, often unable to move when disturbed by unfore-seen circumstances. When in fear, it often sticks out fangs. It often lives in colonies.

feeding ecology and diet

Detects flies and other small insects walking on their silken tubes. Climbs up tube and underneath insect, sticks its fangs through tube wall, and drags prey inside and down into vertical tube to be eaten. Returns later to surface, throws out remains of prey, and repairs hole.

reproductive biology

Mating takes place in tube and they stay together for several months. Then male dies and is eaten by female. Females lay 80–150 eggs in a cocoon resembling a small white bag. Spiderlings take one year to become full-grown and four years to reach maturity. Females may live for more than eight years, with usual range of 2–8 years, slightly less for males.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Spruce-fir moss spider

Microhexura montivaga

order

Araneae

family

Dipluridae

taxonomy

Microhexura montivaga Crosby and Bishop, 1925, Mount Mitchell, North Carolina, United States.

other common names

None known.

physical characteristics

One of smallest spiders, with adults of length 0.10–0.15 in (0.25–0.38 cm). Ranges in color from light brown to darker reddish brown. No markings on abdomen. Carapace is mostly a yellowish brown. Chelicerae are projected forward beyond anterior edge of carapace. Possesses pair of extremely long posterior spinnerets. Second pair of book lungs, which appear as light areas, is posterior to genital furrow.

distribution

Found only at the highest mountain peaks, at and above 5,400 ft (1,645 m) in elevation, in the southern Appalachian Mountains of western North Carolina and eastern Tennessee (Untied States). Recorded from Mount Mitchell, Yancey County, North Carolina; Grandfather Mountain, Watauga, Avery, and Caldwell Counties, North Carolina; Mount Collins, Swain County, North Carolina; Clingmans Dome, Swain County, North Carolina; Roan Mountain, Avery and Mitchell Counties, North Carolina, and Carter County, Tennessee; Mount Buckley, Sevier County, Tennessee; and Mount LeConte, Sevier County, Tennessee. Experts believe that the Mount Mitchell population has been killed off.

Ongoing surveys show that reproducing populations still survive on Grandfather Mountain in North Carolina, but are restricted to small areas of microhabitat. Both the Mount Collins and Clingmans Dome populations, if still present, are extremely small. On Roan Mountain, scattered occurrences have been found at small rock outcrop sites. At Mount Buckley, population is restricted to scattered areas of microhabitat on separate rock outcrop sites within an area of 0.5 acres (0.2 ha) in size. At Mount LeConte, research indicates that the healthiest of the surviving populations occur in four small, separate areas of rock outcrop sites.

habitat

Inhabit damp but well-drained moss and liverwort mats that grow on completely shaded rocks or boulders in mature, high-elevation coniferous (red spruce and Fraser fir) forests. Cannot tolerate extremes of moisture, and excessive gain or loss of moisture within body. The mats cannot be too dry (it is very sensitive to desiccation) or too wet (large drops of water can also pose a threat to it). As a result, it builds tube-shaped webs in interface between mat and rock surface (although sometimes extends into interior of mat) to control amount of moisture within surroundings. Tubes are thin-walled and typically broad and flattened with short side branches.

behavior

Little information is known on its behavior.

feeding ecology and diet

Little information has been collected on feeding habits. No record of prey having been found in webs, nor has it been observed taking prey in the wild, but abundant springtails (tiny, wingless insects) in moss mats provide most likely source of food.

reproductive biology

Little is known about its breeding habits, lifecycle, or life span.

conservation status

Not listed by the IUCN. It is considered Endangered in its entire range by the U. S. Fish and Wildlife Service. It was listed as Endangered under the U. S. Endangered Species Act in February 1995, after research showed that its population size and distribution was limited to only four sites, with only one stable site left. Its populations are believed to be diminishing because of rapid decline of damp, high-elevation old-growth forest habitats (especially the Fraser fir); decline brought about by infestation of exotic insect (balsam wooly adelgid) that has been killing off fir and spruce trees, air pollution brought about by acid rain, and past land use.

significance to humans

Not known to be commercially valuable; however, because of its rarity, it is believed that collectors may seek it out.

Zebra spider

Salticus scenicus

order

Araneae

family

Salticidae

taxonomy

Salticus scenicus Clerck, 1757.

other common names

English: Zebra jumping spider.

physical characteristics

Relatively small- to medium-sized spider, with adult female length of 0.20–0.28 in (5–7 mm) and adult male length of 0.20–0.32 in (5–8 mm). Considered one of most common and well-known salticid spiders. Has very acute vision with distinctive eye arrangement of eight simple eyes (three rows of 4, 2, and 2) that enable it to focus in all directions. First median pair of eyes is largest, located on front of cephalothorax, look forward, and called "headlight" eyes. Posterior eyes are smallest in size, located on top of cehalothorax and look upward. Eyes can move in or out for focusing, and can turn up and

down, and left and right for 360° eyesight (called "integral binocular vision"). Nuclei of retinal cells of anterior eyes have evolved to side, out of the path of light. Can also turn its carapace more than 45° to look around. Considered to have best vision of any arthropod, especially where anterior median eyes are concerned. When eyes become dirty, they are cleaned with front two legs.

Most distinguishing feature is black body that contains white hairs, which form stripes on abdomen. Male is similar to female but with larger chelicerae, darker body color, and brightly colored brushes on appendages. Cephalothorax contains brilliant hairs, stout body, and rather short legs; eight legs are hairy and covered by sensory hairs (trichobothria). Tracheal system extends into cephalothorax. Abdomen contains digestive system, breathing apparatus, and silk-producing organs. Huge chelicerae are usually hidden behind pedipalps.

distribution

Northern Hemisphere, but mostly in northern Europe (and widely distributed throughout England).

habitat

Commonly found anywhere outside where sun is shining; especially in gardens, on rocks, stones, flowers, plant foliage, and grass, and occasionally on trees. Often found on vertical surfaces such as walls, fences, decks, patios, and doorways. At night or during rainfall, it hides in dry spots.

behavior

Diurnal; most active during hottest days of year, mostly in early to late summer. Often attacks and kills much larger adult hobo spiders, which are competitors for food. Jumps more than it walks. Able to jump from standing start; can also jump backward and sideway with equal abilities. This type of motion is used both to capture prey and to avoid capture by predators. Uses third and/or fourth pair of legs for jumping. Whenever it jumps, it will release thick, white, slightly viscid silky line to use as anchor to crawl back to original position. Silk is produced from special organs (spinnerets) at rear of abdomen. Also produces silken bag ("retreat") in such places as crevices, under stones, under bark, and on foliage and plants. Bags used for protection and shelter at night, resting, molting, feeding, protecting young, and during winter to hibernate.

Prey can be noticed from distance of about 12–16 in (30–40 cm), although it is reported that it can see prey up to 8 ft (2.4m) away. At distance of about 7.9 in (20 cm), it turns its body so that front eyes point to victim; eye muscles focus on prey and the eyes move around optical axis. Able to distinguish between prey and predators, and also capable of distinguishing color. After object is recognized as eatable, it carefully moves toward victim.

feeding ecology and diet

Eats primarily insects, but also eats spiders the same size or smaller. It avoids ants. Reported to feed on mosquitoes with lengths almost twice its own. Active hunter, able to catch larger prey primarily because of its excellent eyesight during day (especially in direct sunlight) and excellent ability to jump from a stationary position. Slowly stalks potential prey by creeping very close, usually to within 2.8–5.9 in (7–15 cm). When at reachable distance, it attaches silky thread to substrate, and then jumps on prey and paralyzing it with its venomous jaws. Powerful chelicerae are then used for chewing up prey prior to sucking up liquid contents. Does not make webs for catching prey.

reproductive biology

Males court females by dancing and displaying brilliant colors, distinctive marks, and bright appendages. Males deposit sperm on small web to be used as special reservoir within pedipalp to carry seed around. They will then try to mate with females. Mating is dangerous for males, having to convince females that they are prospective mates and not prey. This activity involves various motions with front legs and moving abdomen up and down. (The more they move, the more likely they will be noticed and accepted by female.) During this time, males try to reach reproductive organ of female (epygine), located under abdomen. When sperm is successfully transferred to female, she will carry it in special compartment and use it when she is ready to fertilize eggs. Females lay their eggs in small silky bags mostly in spring and summer for the purpose of being able to protect spiderlings from predators. Females will guard young until they are ready to leave, normally after second molting period. Young usually mature in late spring and summer. Lifecycle is about one year.

conservation status

Not listed by the IUCN.

significance to humans

Often considered a pest to humans, but it is actually harmless.

Common harvestman

Phalangium opilio

order

Opiliones

family

Phalangiidae

taxonomy

Phalangium opilio Linnaeus, 1758.

other common names

English: Harvest spider.

physical characteristics

Small, globular (rounded) body and very long thin legs. One major body section, eight legs, no antennae, no web spinning (silk-producing) organs, and no poison (venom) glands. Adult length is 0.14–0.35 in (3.5–9.0 mm), with males generally smaller than females. Upper body surface colored with indistinct and variable light gray to brown pattern, and lower body surface is usually light cream. Possesses two eyes located in middle of body, forcing it to look outward from sides.

distribution

North America, Europe, and temperate Asia.

habitat

Commonly found in relatively disturbed temperate habitats such as crops of alfalfa, cabbage, corn, grains, potatoes, and strawberries. Also found in wide variety of undisturbed temperate habitats, including forests, brushy areas, and open grasslands.

behavior

Generally takes prey with its long legs as it flies by. It is active throughout summer, but most active in later summer and fall. Nocturnal, often gathering in large groups on tree trunks and interlace legs together. It uses its scent glands located on either side of body to produce peculiar smelling (but non-poisonous) fluid when it is disturbed, probably acting as a repellant to some predators. Will also intentionally detach a leg, leaving it twitching, to distract predator; this is only done in desperate situations, because detached leg is permanently lost.

feeding ecology and diet

Omnivorous, feeding on many soft-bodied pest arthropods found in crops, such as aphids, caterpillars, leafhoppers, beetle larvae, mites, and slugs. Also feeds on dead insects and other decaying plant material like rotted fruit, as well as earthworms, harvestmen, spiders, and other beneficial invertebrates. Can be cannibalistic.

reproductive biology

Females lay clusters of eggs in moist areas on the ground, often under rocks, in cracks in soil, or between soil and crowns or recumbent leaves of plants. Number of eggs laid from 10 to several hundred. Eggs are generally laid in fall where they over-winter, and then hatch following spring. (In Europe, they reproduce once each year, with eggs over-wintering. In parts of North America, two or more generations may occur, with eggs, immature young, and adults often over-wintering.) The eggs hatch in 3–20 weeks or more, depending primarily on temperature. Eggs are spherical, about 0.0158 in (0.4 mm) in diameter, with a smooth surface and color changing from off-white to dark gray-brown as they mature. After hatching, immature young are similar to adults, only smaller and with legs shorter relative to body size. Immature young undergo several molts (usually seven) and reach maturity in 2–3 months, again depending on temperature.

conservation status

Not listed by the IUCN.

significance to humans

It helps to control pests that feed on cultivated crops, helping to keep pest densities low. It also feeds on dead insects and other decaying material. It is medically harmless to humans.

Long-bodied cellar spider

Pholcus phalangioides

order

Opiliones

family

Pholcidae

taxonomy

Pholcus phalangioides Fuesslin, 1775.

other common names

English: Cobweb spider, daddy longlegs spider, long-legged cellar spider, shepherd spiders, harvest spiders.

physical characteristics

Characterized by eight long legs and spider-like appearance; length of 0.25–0.50 in (6.4–12.7 mm) with front legs about 1.75–1.94 in (45–50 mm) long, small bodies that are grayish brown or tan in color, and very long, somewhat translucent, skinny legs. Males are slightly shorter than females; fragile with a rectangular, elongated abdomen (oval-shaped body). Head, thorax, and abdomen are fused, with elongated, cylindrical abdomen about three times longer than wide. Chelicerae are fang-like.

distribution

Throughout world, but found primarily in the United States and Europe.

habitat

Often found in dark, damp areas such as crawl spaces, basements, closets, sink cabinets, ceilings, cellars, warehouses, garages, attics, and sheds. Also found near open doors and other similar entrances that allow flying insects to enter. Often lives upside down in stringy, irregular webs that are not cleaned, but are continually added to with new webbing, resulting in extensive web networks.

behavior

Web (also called "net") is large, irregularly arched construction that looks similar to canopy. The spider resides on lower side hanging upside down within web. When disturbed, it will shake web violently. Anything that touches net is attacked and taken for prey, if it is not too large. Uses net as means of camouflage by whirling its body around with legs firmly attached to net. If it accidentally falls from web, it runs in a wobbly fashion, so as not to be seen easily. Once web becomes old and unusable, it constructs additional webbing attached to old web. Enemies are birds, wasps, and humans.

feeding ecology and diet

Predator and carnivore, eating almost any kind of insect or bug. Eats moths, mosquitoes, flies, gnats, and beetles that have become entangled in silky web. Will invade spiders' webs, attack resident spider, and take over web. If prey is already enwrapped in web, it eats it. New prey trapped in web will be swiftly wrapped with new silk, spun as many as several feet (meters) around victim by fourth pair of legs. The prey is then bitten, with digesting fluid injected into body. It will then proceed to suck body empty over the course of a day or two. When it is finished, it will cut remains loose, letting them fall to ground in pile of dead bodies.

reproductive biology

Often lives close to mate; commonly living next door to each other. Mating can take up to several hours to complete. During process, male sperm is transferred to female by way of special cavity at beginning of uterus. Resulting spermatozoa remain in cavity until used to fertilize eggs. Time of fertilization depends largely on availability of food sources in area. Female will wrap eggs in clear sac that she keeps in her mouth (between chelicerae) for safety. Up to three sacs may be produced, each containing 13–60 eggs. Female will guard eggs until prenymphs hatch from eggs after several weeks. After about nine days, prenymphs shed old skins and tiny spiders appear; they soon leave maternal net to look for new place to build their own net. They will continue to shed their skin as they grow, with five molts needed to reach maturity. Lives for about two years.

conservation status

Not listed by the IUCN.

significance to humans

Not dangerous and actually is quite beneficial in that it captures and eats many types of insects that are considered pests and poisonous spiders, including black widow and brown recluse spiders.

No common name

Eukoenenia draco

order

Palpigradi

family

Eukoeneniidae

taxonomy

Eukoenenia draco Peyerimhoff, 1906.

other common names

None known.

physical characteristics

Small (less than 0.12 in [3.0 mm] in length), can grow up to 0.11 in (2.8 mm) long, but usually are 0.0394–0.0787 in (1.0–2.0 mm) in length. It is light yellow to white, being almost colorless; has many-segmented, whip-like post-abdomen and a wide pre-abdomen. Chelicerae are thin, long, and pincer-like (chelate), with three articles and lateral moveable finger. Mouth is located at tipped end of prominent protuberance. A labium is present.

It does not have eyes, a respiratory system, or a circulatory system, but does have innervated setae that detect vibrations. Receives oxygen through very thin and colorless cuticles. No Malpighian tubules but, instead, pair of excretory coxal glands. It has carapace (propeltidium) divided in three pieces, with 11 defined segments in abdomen and four parts in sternum. The prosoma is covered by two free tergites and is attached to opisthosoma by pedicel; opisthosoma has anterior mesosoma and short posterior metasoma possessing a flagellum with many articles. Other appendages are leg-like. Pedipalpal coxae are not part of preoral cavity, and are similar to leg coxae. Several sternites are present. The first leg, used as a feeler, is positioned distally, and possesses many articles.

distribution

Scattered throughout the world, primarily in warmer climates. (Specific distribution unknown; no map available.)

habitat

Generally located in tropical regions, commonly found under rocks, half-buried stones, and sometimes in caves. During drier times, it sometimes digs under soil. Specifically, little about its habitat is known.

behavior

It walks with first legs stretched forward in front. During drier seasons, it sometimes descends into soil. Little of its specific behavior is known.

feeding ecology and diet

There is some research evidence that it feeds on eggs of other small animals in vicinity. However, few specifics are known about its ecology and diet.

reproductive biology

Males produce a spermatophore. Little of its specific reproductive biology is known.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Book scorpion

Chelifer cancroides

order

Pseudoscorpionida

family

Cheliferidae

taxonomy

Chelifer cancroides Linnaeus, 1758.

other common names

English: House scorpion.

physical characteristics

Slightly smaller than scorpions, with a length of 0.10–0.18 in (2.6–4.5 mm). Does not possess stinging tail, has enlarged pedipalps, and transmits spermatophore in complex courtships. Cephalothorax (also called scutum) contains six pairs of appendages: chelicerae, palpal chelae (two well-developed claws), and four pairs of legs. Femora of legs one and two are different in general structure, especially with regards to joints, from femora of legs three and four. Cephalothorax is olive-brown to dark red. Palpal chelae (reduced claws near mouth) consist of large bulbous hand, with one fixed finger and one moveable finger. Moveable finger does not have edge but instead has a subapical lobe. Accessory teeth are not contained on chelel fingers. Opisthosomal tergites are pale brown to olive-green, with darker spots. Pedipalps are tawny brown to reddish brown, with some olive coloration. Venom apparatus is well developed in both fingers of palpal chela. Cheliceral flagellum consists of three long, straight setae. Complex internal genitalia of males are heavily sclerotized. Spermathecae of females are short, rounded sacs, with sclerotic plates.

distribution

Throughout most of Europe.

habitat

Usually found under stones, beneath bark of trees, or in vegetable debris, but can also be found in human habitations and outbuildings such as stables, barns, grain stores, factories, and houses, and seems to move wherever humans locate. Often found in old books (thus, its common name). Prefers warmer regions of the world.

behavior

Often found in groups of several dozens. Females often use pedipalps to hold onto flying insects such as houseflies to be carried to where it wants to go. Males do not commonly use this method of transportation (called phoresy). Palpal chelae are mainly used for defense/fighting, acquisition of prey, and moving small objects (like sand grains) to make nests. A small, spherical silken chamber (or cocoon) is built for hibernation during winter months, and for molting.

feeding ecology and diet

Carnivore and insectivore, eating animal tissue and arthropods such as small insects, mites, and lice. Often secures itself underneath wings of large tropical beetles to feed on parasitic mites. It may also do similar actions to legs of houseflies and other two-winged insects. Generally will grab prey with pedipalps, immobilize prey with poison glands, rip it up with chelicerae, and suck fluids from body.

reproductive biology

Complex courtship and mating behaviors from both males and females, including extension of ramshorn organs of male and dance-like behavior by pair. Reproduction is through spermatophore: adult males use modified first legs to expel mass of spermatozoa. Females are oviparous; they will build nest by secreting a "brood sac" attached to body, where she will nourish young. Generally, 16–30 offspring are produced from each reproductive cycle; they will depart the mother's protection soon after hatching, after reaching a fixed, definite shape. Sexual maturity is reached in 1–2 years.

conservation status

Not listed by the IUCN.

significance to humans

Often eats lice that have infected human hair. Also feeds on other creatures seen as pests for humans, such as mites and ants. It seems to offer little direct benefit to humans, although little is really known about its contribution to human life.

No common name

Ricinoides afzelii

order

Ricinulei

family

Ricinoididae

taxonomy

Ricinoides afzelii Thorell, 1892.

other common names

None known.

physical characteristics

Heavy-bodied, usually 0.12–0.20 in (3–5 mm) in length, but can reach up to 0.39 in (10 mm) long. It possesses thick exoskeleton along with cucullus (transverse hood-like flap) that covers mouthparts, and can be raised and lowered and is located at anterior edge of carapace. Prosoma is covered by carapace and is widely connected to opisthosoma, which narrows at front, forming pedicel (waist), where it is attached to prosoma (or cephalothorax). At the end of abdomen, tubucles stick out, forming anus. Chelicerae terminate into two articles that form scorpion-like pincers. Smallish pedipalpi are leg-like and also end in medium-sized pincers. Ventral and coxal endites are

fused to form trough, posterior wall of postoral cavity. Leg coxae cover venter of prosoma. Short and heavy legs have no modifications except in third pair of males, which are modified to form copulatory organs. It has no eyes, and is poorly equipped with any type of sense organs. Male organs are found on metatarsus and tarsus of third pair of legs; metatarsus and first two segments of tarsus are modified by cavities and by fixed and moveable processes. Excretory organs consist of Malpighian tubules and pair of coxal glands. Circulatory system is degenerate; it has no lungs, and gas exchange takes place through trachea.

distribution

Scattered in tropical West Africa.

habitat

Dwells within soil, usually in tropical leaf litter.

behavior

Slow-moving creature that requires dampness to survive. Little about its behavior is known.

feeding ecology and diet

Predator that feeds on tiny invertebrates and other arthropods in caves and leaf liter. Specific information on its feeding ecology and diet is sparse.

reproductive biology

Males mount the backs of females, fourth legs grasping her opisthosoma. Both face same direction during reproduction. Male uses third legs to transfer sperm (possibly through spermatophore) to female's genital opening (via insemination). There is assumed to be no courtship. Normally, 1–2 eggs are laid. Eggs are carried under mother's hood, until young hatch into six-legged larvae, with subsequent molts being protonymph, deutonymph, tritonymph, and adult. About 1–2 years is taken to reach maturity, with lifespan of 5–10 years.

conservation status

Not listed by the IUCN.

significance to humans

None known.

No common name

Agastoschizomus lucifer

order

Schizomida

family

Protoschizomidae

taxonomy

Agastoschizomus lucifer Brusca and Brusca, 1990.

other common names

None known.

physical characteristics

Very small, less than 0.39 in (10 mm) in length, but usually averages only 0.12 in (3.0 mm) in length. Does not have eyes. Has divided prosoma covered anteriorly by propeltidium and by two free tergites: the mesopeltidium and metapeltidium. One-third to one-tenth its greatest dimension separates large mesopeltidia. Short abdominal flagellum is located on last abdominal segment. Flagellum is segmented in females. Abdomen has eight pairs of dorsoventral muscles, which are not flattened. Chelicerae lack a serrula, but have two blunt hemispherical knobs. Has fixed digit with two teeth, and no setae at base. Basitarsal spurs are symmetrically located, about one-third to one-half dorsal length of basitarsus. Feeler-like first legs are used for sensory purposes. Lacks patellae. Tarsi have eight pieces and no claws. Trochanter of fourth leg is about 2.2 times longer than wide; fourth femur is 3–5 times longer than wide. Anal glands are present. One pair of book lungs.

distribution

Mexico.

habitat

Usually caves in the tropics, living in leaf litter or under stones. Digs tunnels in soil.

behavior

Can move backward rapidly with use of enlarged femora. Believed to be able to produce defensive chemical smell by means of repugnatorial glands.

feeding ecology and diet

Predator, but little information is known about specific prey.

reproductive biology

Female hooks chelicerae into dilations of male's flagellum. Then, male deposits spermatophore to substrate and pulls female over it. Afterwards, female lays 6–30 eggs, which are attached to ventral abdomen (gonopore) until they hatch. They have one embryonic and five postembryonic instars. Mature in 2–3 years.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Striped scorpion

Centruroides vittatus

order

Scorpiones

family

Buthidae

taxonomy

Centrurus vittatus (Say, 1821).

other common names

English: Common striped scorpion, striped bark scorpion.

physical characteristics

Maximum length of 3 in (7.6 cm), but average about 2.4 in (6.1 cm). Characterized by dark triangular mark on front part of head region in area over median and lateral eyes, and pair of blackish, parallel, longitudinal stripes on upper surface of abdomen. Long, slender tail is longer in males than in females. Adult body color varies from yellowish to tan. Young are usually lighter in color, with last body segment and bases of pedipalps being dark brown to black. Has slender pedipalps and a long, slender tail.

distribution

Found in southwestern United States, being most heavily concentrated within the state of Texas and outward to Oklahoma, Louisiana, Arkansas, western Mississippi, extreme western Tennessee, southern half of Missouri, southern tip of Illinois, eastern tip of Kentucky, Kansas (except northwestern part), tip of south-central Nebraska, northeastern part of Arizona, southeastern part of Colorado, and New Mexico (except southwestern part); also found in northern Mexico, within the states of Tamaulipas, Coahuila, Nuevo León, Chihuahua, and Durango. Considered the most common scorpion species in the United States.

habitat

Found in diverse environments, being very adaptive. Mostly found in areas containing many cracks and crevices such as diverse regions of rocky areas, forests, and buildings; also found in relatively open areas such as grasslands and sand dunes. Often found in close association with humans, being commonly found indoors; often found in damp, cool areas around dead vegetation, boards, rocks, and fallen logs; often found climbing trees and walls, and are common in house attics. During the day, it usually hides under loose rocks, bark, and leaves.

behavior

Ecomorphotype, meaning it actively moves while foraging; moves easily over vertical surfaces and clings to undersides of objects; but does not burrow. It remains in shelters during day, becoming active at night. This schedule helps it to maintain water and body temperature balance. It also dwells in crevices, willing to use any kind of crevice for protective retreat. Is able to tolerate many different climates such as very low and very high temperatures. Its venom toxicity is low.

feeding ecology and diet

Primarily insectivorous, eating small arthropods such as beetles, centipedes, crickets flies, spiders, and other small insects. It normally hunts at night by depending on its acute sense of touch and smell. Feathery, comb-like chemical receptor organs (called pectines) located on underside between last pair of legs touch ground as it walks, helping it to track prey. When finding prey, it grabs it and crushes it with powerful pinchers. Tail is then brought over body to sting victim. This paralyzes prey, which soon dies. It will then chew prey into semi-liquid state, which can then be sucked up into tiny mouth.

reproductive biology

Mating occurs primarily in spring and early summer. Has elaborate courtship ritual, which can last for hours. Female and male will grasp each other's pincers and jaws, and dance back and forth. Eventually, male deposits spermatophore on the ground and pulls female to it. She picks up the sac with a special organ on abdomen to fertilize it. Its gestation period and maturity period varies, depending on climatic and environmental conditions, with shorter periods for each in warmer parts of habitat. Embryos are nourished in female's body through placental connection. Probably has gestation period of 6–12 months, with maturity period probably of 1–2 years. Females give birth to up to 50 young at one time, but averages about 30. After birth, young climb on mother's back and soon molt. After first molt, they disperse and lead independent lives. They molt an average of six times before maturity.

conservation status

Not listed by the IUCN.

significance to humans

Can inflict a very painful sting and causes extreme discomfort if touched or grabbed by a human, but it is not considered as dangerous as some of its relatives. It usually causes only minor medical problems such as local swelling and discoloration to healthy humans. If death occurs, it is because of anaphylactic shock, not from the direct toxic effects of venom. It helps control local insect populations.

Emperor scorpion

Pandinus imperator

order

Scorpiones

family

Scorpionidae

taxonomy

Pandinus imperator Koch, 1841.

other common names

None known.

physical characteristics

Has large, well-developed pincer-like pedipalps, is uniformly covered with hard cephalic shield or carapace, and has prehensile tail armed with a stinging apparatus; usually attains lengths (including tail) of 5–7 in (12.7–17.8 cm) and weighs about 1.1 oz (35 g), but can reach length of 8 in (20.3 cm) and weight of 2 oz (57 g); pregnant females usually weigh over 1.4 oz (40 g) (considered one of the largest scorpions, but not among the heaviest). As adult, males and females act and look similar; however, males are usually narrower or smaller. Has exoskeleton color of glossy dark blue or black, but some may be dark brown and occasionally even greenish; dark color acts as camouflage. Two pedipalp chela (pedipalps) have reddish brown color, and are very granular in texture. There are numerous, clearly visible sensory hairs on the pedipalps, metasoma (tail), and telson (stinger). Tail is long and made up of six segments, ending in large telson, which contains venom glands. Telson terminates in sharp curve, which serves as stinger, and is reddish brown in adults and yellowish in young. Telson of second instar is white, but soon becomes darker after each molt. Four-sectioned thorax contains pair of legs on each section, specifically on undersurface, making total of eight legs (four pairs). Behind fourth pair of legs are ventral comb-like structures known as pectines; males can be also distinguished from females by their longer pectines.

distribution

Western Africa, primarily in Senegal, Guinea-Bissau, Guinea, Côte d'Ivoire, Sierra Leone, Ghana, Togo, Democratic Republic of Congo, Nigeria, Gabon, and Chad.

habitat

Lives in tropical forests, rainforests, and savannas, preferring hot, humid environments. Lives in empty or self-made burrows up to 12 in (30 cm) in length. Often found beneath rocks, logs, tree roots, or vegetation debris.

behavior

Sensitive to light, so is primarily nocturnal. It is unusually docile and very slow to sting. Although young use stingers in normal fashion, adults rarely use stinger to subdue prey. They prefer to kill prey with massive claws. Even when stinging in defense, adults may not inject venom. Mothers and young/siblings often live together. Mothers are occasionally cannibalistic, being known to eat a few of their young when necessary. It likes to burrow beneath soil.

feeding ecology and diet

Feeds on almost anything that is smaller in size, including arachnids, crickets, insects, small lizards, mealworms, millipedes, and small mice. Young eat pinhead crickets and other small insects. It does not generally pursue prey, but waits for unsuspecting insects and other small animals to pass by. Its eyes, which cannot form sharp images, are of little use in detecting prey. Air and ground vibrations are used primarily in determining the position of prey. When hungry, however, it moves slowly forward supported by its hind legs, with claws open and extended, and tail raised and pointed forward. It quickly strikes with stinger or grasps victim. Larger individuals rarely use stinger to capture prey; instead, they crush it with claws. Smaller and younger ones rely on stinger to subdue prey. They must predigest their food before they consume it. Once prey is subdued, they secrete digestive enzymes onto prey, which liquefies the food and readies it for consumption.

reproductive biology

Males spend the majority of time looking for mates. Mating can occur year-round, but warm temperatures are required. When mating, male holds female in grasp, holding and pushing her around until finding suitable place to deposit spermatophore onto a solid substrate. He then pulls female into position over spermatophore, and she accepts it into her genital aperture. Male leaves quickly, to avoid being eaten. It is viviparous (embryos develop within mother, gaining nutrients for growth directly within specialized sacs on female's overiuterus). A highly specialized structure connects embryo's mouth to female's digestive system. Gestation period is 7–9 months. Very tiny young are born alive, with a litter of 9–35. Parental care seems important. Young stay on mother's back, as she protects and cares for them, with increased survival probabilities while in family groups. Young are white at first, but become darker after each molt. They grow and shed entire exoskeleton several times before they are full-grown. They reach sexual maturity at around four years after seven molts. They have a lifespan of about eight years.

conservation status

Not listed by the IUCN. Because of years of potential over-collection, it has been placed on the CITES Appendix II list (as Threatened) to monitor populations. Primary enemy is humans, who may have one as a pet.

significance to humans

Although large in size, it is not considered dangerous to healthy humans. Its venom is mildly venomous, with a painful sting. It has very strong pedipalps, which can give very painful pinches. Adult males will rarely sting, but young individuals and females with young can be more likely to sting. They are the most common scorpion in captivity, with many exported from western Africa each year.

Egyptian giant solpugid

Galeodes arabs

order

Sopugida

family

Galeodidae

taxonomy

Galeodes arabs Koch, 1842.

other common names

English: Desert camel spider.

physical characteristics

Measures up to 4.7 in (12 cm) in length with legs and only 2 in (5 cm) with body. Males are smaller and lighter than females, but have longer legs. Both sexes are yellowish in color. Has eight legs (four pairs), and body is in two parts: prosoma and opisthosoma (which has no pedicel, and consists of 11 somites). Has very powerful chelicerae; pedipalpi do not end in a claw but rather in a suctorial organ, and first pair of legs is long and thin, and not used for walking but as feelers. Bodies and legs are hairy. Respiratory system contains well-developed tracheal system. Has very long legs, terminal anus, and exterior lobes of propeltidium are fused posteriorly. Male cheliceral flagellum is a single, capitate (terminally enlarged), paraxially moveable seta located on mesial surface. Female operculae are not differentiated from other abdominal sternites and are not variable. Two eyes are placed on small projection near fore-edge of propeltidium.

distribution

Northern Africa and the Middle East, especially in the Sinai Desert.

habitat

Lives in sandy arid and desert environments.

behavior

Generally nocturnal creature, however still active during day (but avoiding direct sunlight). During day, spends most time hiding in burrows or under objects looking for shade. Able to run very fast, up to 20 in (50 cm) per second for short periods of time, though unable to sustain this pace for long periods. Considered one of the fastest arthropods. Uses rear three pairs of legs to run, and uses first pair for sensory purposes (as "feelers" to detect and pull prey into its large oversized jaws). Constructs extensive, shallow burrows under bushes and buildings by utilizing chelicerae, pedipalpi, and metatarsal and tibial rakes of second and third pairs of legs. Burrows are used for mating, defense, and shelter. Can stridulate (make a noise) by rubbing together pair of horny ridges on insides of chelicerae.

feeding ecology and diet

Exclusive carnivore, aggressively feeding on small mice, lizards, amphibians, spiders, scorpions, some small birds, and other similar animals. Hunts and feeds at night, using ground-level vibrations to detect prey. Pedipalpi are most active organs, used to pick up prey (often termites and other prey). Uses its large chelicerae not only to crush often larger prey, but also to scoop water into its mouth when drinking.

reproductive biology

It mates with quick but strenuous action. Male seizes female with his legs and chelicerae, grasping her body but rarely hurting her. The caresses of his legs then so strongly affect her that she falls into a motionless hypnotic state. He then picks her up in his chelicerae and carries her to a suitable location. Next, he lays her on her side and awakens her sexually by stroking underside of her abdomen. Males do this because females will often eat male partners if they are too slow in leaving after mating. Reproduction is through spermatophore, which male produces during courtship, deposits on ground, and transfers into female gonopore with his chelicerae. She digs a deep burrow to deposit egg masses that may contain 5–164 eggs. Females may lay 1–5 egg masses. Eggs take 1–2 days to hatch. Once hatched, young remain in burrow for first two molts. First instar larvae (first "stadium") is non-moving, embryo-like creature that later molts into more active animal that looks like small adult.

conservation status

Not listed by the IUCN.

significance to humans

Does not possess venom and prefers to stay away from humans, so presents little or no concern to humans.

Giant whip scorpion

Mastigoproctus giganteus

order

Uropygi

family

Thelyphonidae

taxonomy

Mastigoproctus giganteus Lucas, 1835.

other common names

English: Desert whip scorpion, giant vinegaroon, grampus.

physical characteristics

Possesses long, thin, whip-like tail instead of stinger, and has large anal glands that discharge strong defensive acids. Length about 1.0–3.2 in (25–80 mm), not including tail, and is reddish or brownish black. Both males and females are similar in appearance, with heavy pedipalps that are formed into pincers. Carapace covers body. Has one pair of eyes, located in front of cephalothorax, and six more eyes, three off each side of head. Even though it has eight eyes, it has poor eyesight; compensates by being able to detect ground vibrations, especially those by prey. Two chelicerae (normally turned forward) are used to grasp, tear, and transfer food into mouth. Has four pairs of legs, with front-most (first) pair longer and thinner than other three pairs; first pair of legs is used to detect prey and evaluate environment (like sensory feelers), while other three pairs of legs are used for walking. Inside abdomen are two pairs of layered lungs with a whip-like telson that is usually held curled toward back; telson is used for defense, and is capable of spraying acetic and caprylic acids that originate from repugnatorial glands near anus.

distribution

Found throughout southernmost states in the United States; however, is more likely found in southwestern United States, especially in the Trans-Pecos region of Texas but also as far north as the panhandle of Texas and in south Texas, and in northern Mexico.

habitat

Commonly found in chaparral and deserts, but has also been found in grassland, scrub, pine forests, and mountains. Usually uses underground burrows for home. Also is found in burrows under logs, rotting wood, rocks, and other natural debris. Prefers humid, dark places and avoids sunlight whenever possible.

behavior

Nocturnal, with little action seen during day. At night, it is active predator, finding prey by detecting ground vibrations to trap prey. Although basically passive, it has its own defense mechanisms that are very effective. If disturbed or in danger, it will squirt acid capable of eating through exoskeleton of invertebrates, enabling it to escape enemies or to capture prey. Uses chelicerae to pinch.

feeding ecology and diet

Feed offs many different types of insects, including crickets and roaches. Uses ground vibrations to detect movements of prey, and then uses foremost pair of walking legs, the feelers, to find prey. Uses feelers to make sure prey is surrounded and still, and then uses chelicerae, its pinchers, to pinch and capture prey. Some acid may be squirted out to kill prey. Mouthparts are used for chewing.

reproductive biology

During reproduction, sperm is transferred indirectly when male deposits spermotophore, or sperm sac, on the ground. He then gently guides female over it by grasping her sensory pedipalps. He may then assist her in taking spermatophore into her genital opening by using his pedipalps. Afterwards, female will take to a sheltered spot, carrying eggs in a silken sac until they hatch. Colorless young then climb and ride on her back until they molt. They then become independent.

conservation status

Not listed by the IUCN.

significance to humans

Kept as pet and is helpful in controlling roach and cricket populations. Non-poisonous but can pinch and is capable of spraying a mist of concentrated acetic acid when disturbed by humans or other creatures.

Resources

Books

Adis, J., and M. S. Harvey. "How Many Arachnida and Myriapoda Are There Worldwide and in Amazonia?" In Encyclopedia of Biodiversity. New York: Academic Press, 2000.

Beacham, Walton, Frank V. Castronova, and Suzanne Sessine, eds. Beacham's Guide to the Endangered Species of North America. Detroit, MI: Gale Group, 2001.

Bosik, J. J. Common Names of Insects and Related Organisms. Lanham, MD: Entomological Society of America, 1997.

Cloudsley-Thompson, J. L. Spiders, Scorpions, Centipedes and Mites. Oxford, U.K.: Pergamon Press, 1968.

Foelix, Rainer F. Biology of Spiders. Cambridge, MA: Harvard University Press, 1982.

Levin, Simon Asher, ed. Encyclopedia of Biodiversity. San Diego, CA: Academic Press, 2001.

McDaniel, Burruss. How to Know the Mites and Ticks. Dubuque, IA: William C. Brown Company Publishers, 1979.

Milne, Lorus, Lorus J. Milne, and Susan Rayfield. The Audubon Society Field Guide to North American Insects and Spiders. New York: Knopf, 1980.

Parker, Sybil P., ed. Synopsis and Classification of Living Organisms. New York: McGraw-Hill Book Company, 1982.

Polis, Gary A., ed. The Biology of Scorpions. Stanford, CA: Stanford University Press, 1990.

Savory, Theodore. Arachnida, 2nd ed. London and New York: Academic Press, 1977.

Tudge, Colin. The Variety of Life: A Survey and a Celebration of All the Creatures That Have Ever Lived. Oxford and New York: Oxford University Press, 2000.

Woolley, Tyler A. Acarology: Mites and Human Welfare. New York: John Wiley and Sons, 1988.

William Arthur Atkins