Chilopoda (Centipedes)

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Chilopoda

(Centipedes)

Phylum Arthropoda

Class Chilopoda

Number of families 21

Thumbnail description
Multi-legged predatory arthropods, mostly solitary and nocturnal, found in leaf litter and other cryptic terrestrial biotopes

Evolution and systematics

The class Chilopoda includes five orders, 21 families, and 3,200 known species. Chilopoda belongs to the subphylum Myriapoda, which also includes millipedes (class Diplopoda) and two less diverse groups, the Pauropoda and Symphyla. The structure and function of the head endoskeleton and the mandible suggest that Myriapoda is a natural group, but some zoologists consider millipedes, pauropods, and symphylans to be more closely related to insects than to centipedes.

Four of the five living orders of centipedes share flattened heads and other adaptations for living in confined spaces, and the openings of the tracheal respiratory system are located above the legs on each side of the body. These features indicate that there is a more recent shared ancestry for the orders Lithobiomorpha (1,500 species), Craterostigmomophora (one or two species), Scolopendromorpha (550 species), and Geophilomorpha (1,100 species) than is shared with the order Scutigeromorpha (80 species). The latter group, also known as Notostigmophora, has a domed head, large multifaceted eyes, and the openings of the tracheae are located on the upper side of the body at the back of each tergal plate. Scutigeromorphs have special tracheal lungs. It is only in the orders Scolopendromorpha and Geophilomorpha that hatchlings emerge from the egg with their full adult number of segments. This so-called epimorphic development, the distinctive structure of the testes, and the tracheae having connections between the segments all indicate that these two orders are most closely related.

The earliest fossil centipedes are from the late Silurian (418 million years ago) of Britain, and belong to the order Scutigeromorpha. Other Paleozoic centipedes include the extinct order Devonobiomorpha (one species: Devonian, New York State), and late Carboniferous members of Scolopendromorpha and Scutigeromorpha. Fossils preserved in Tertiary amber are essentially modern.

Physical characteristics

Centipede adult length ranges from 0.15 to 11.8 in (4–300 mm). The head has one pair of slender antennae, composed of 14 to more than 100 articles. Eyes are either faceted (Scutigeromorpha), or composed of one ocellus or a cluster of ocelli on each side of the head (most Lithobiomorpha and all large Scolopendromorpha), or completely lacking eyes (all Geophilomorpha, many smaller Scolopendromorpha). The mouthparts include a pair of mandibles and two pairs of maxillae. The first trunk legs are modified as mouthparts (maxillipedes) that become a functional part of the head. The maxillipedes contain a poison gland, with the venom injected through an opening near the end of the fang. The trunk has 15–191 pairs of legs, with one pair per segment, of which the last pair is usually the only one that is significantly modified: the last pair of legs has a sensory, grasping, or defensive function. The legs have six main segments, including coxa, trochanter, prefemur, femur, tibia, and a one- or two-part tarsus, and a terminal claw. Respiration is by tracheae, which are usually finely branched. The genital opening in both sexes is at the posterior end of the trunk.

As in other arthropods, the heart is dorsal and tubular, extending into the head as the aorta. The ventral nerve cord has paired ganglia in all leg-bearing segments. The brain is tripartite, as in insects. The gut is divided into an esophagus, midgut, and hindgut. The main excretory organs are a pair

of Malpighian tubules that originate at the junction of the midgut and hindgut. An elongate ovary or testes run through much of the trunk. In both sexes, paired accessory glands originate at the genital atrium, at the rear end of the body.

Segments are of uniform length along the trunk on the underside of all centipedes. In all orders except Geophilomorpha, the tergal plates alternate between long and short along the trunk, except for between the seventh and eighth leg-bearing segment, where two long tergites occur in sequence. The tracheae open to spiracles that are confined to segments with long tergites, but are present on all trunk segments, except the last in Geophilomorpha. The number of leg pairs in centipedes totals to an odd number.

Color is highly variable. Most centipedes are drab, with the head and tergal plates yellow or brown (most Geophilomorpha and Lithobiomorpha). Large Scolopendromorpha are often brightly colored, often with a dark band across each tergal plate; in this order, the head and legs may be a different color than the trunk tergites.

Distribution

They occur worldwide, except Antarctica. Some species have become more widespread as a result of commerce and plant introductions, carried in soil or with plants. Some species have disappeared from islands with the introduction of exotic mammals and snakes.

Habitat

Centipedes are common in wet forest and woodland, but many species inhabit dry forest, and some live in grassland or deserts. Some Geophilomorpha hunt in seaweed clusters in the littoral zone. Other species show a preference for caves; a few are confined to caves. Centipedes tolerate an elevational range from sea level to high mountain peaks, even for a single species.

Some species have quite specific microhabitats (such as rotting logs), but most thrive in a range of microhabitats, e.g., logs, bark, litter, or under stones.

Behavior

Centipedes are solitary, except for when brooding eggs or young. Contacts between members of the same species are often aggressive (sometimes even cannibalistic) or involve avoidance rituals. One genus of seashore geophilomorph is

seen to hunt in packs, with numerous individuals feeding on the same barnacle or amphipod crustacean.

Fertilization is external, involving the transfer of a sperm packet that the female picks up with the back of her body and inserts in her genital atrium. The sexes are distinguished in Scutigeromorpha, Lithobiomorpha, and Geophilomorpha by differences in their gonopods (leg-derived structures at the back of the body). Many species have secondary sexual characteristics in the last pair of legs.

Some rituals are primarily defensive such as scolopendrids displaying the last leg pair outspread. Luminescence in some Geophilomorpha is produced by secretions from the sternal glands, which contain noxious chemicals that deter predators.

Few species are seen aboveground by day, and most are more active at night. Scutigeromorphs are inactive for long periods of time while waiting for prey. Other species show bursts in activity (e.g., captive Scolopendra is active for 1–2 hours on average each eighth night).

Species may inhabit deeper levels of the soil or litter during drier seasons. Some species migrate from litter to logs seasonally; seasonal migration between different forest types may occur over a small spatial scale. Apart from short-term occupation of a burrow, territoriality is unknown.

Feeding ecology and diet

Prey, which are typically other soft-bodied arthropods (including other centipedes) or worms are mostly taken alive. Large Scolopendridae can take mice, toads, birds, lizards, geckos, and small snakes as prey. Some geophilomorphs accept plants as food if denied animal prey for long enough.

Prey are often detected by the antennae, which are covered with dense mechanosensory and chemosensory hairs. The eyes do not seem to play a major role in prey detection. In some species, the last pair of legs is also used to detect or grab prey, and may be modified as pincers.

Prey are immobilized by venom injected from the maxillipede fang. The prey are held by the maxillipedes and sometimes also anterior walking legs, passed to the mouth by the first and second maxillae, and then cut up by the mandibles, which have a row of paired teeth in all centipedes, except Geophilomorpha. Geophilomorph mandibles sweep and rasp food. Salivary glands make secretions that break down the prey.

Reproductive biology

Most species have separate sexes, but some are parthenogenetic (female clones) throughout parts of their geographic range. Males have courtship rituals to entice the female to pick up a spermatophore, which is deposited on a web spun by the male in all centipedes, except Scutigeromorpha. A male initiates courtship, tapping the female's posterior legs with his antennae; this tapping ritual may last many hours. The female touches the web with the posterior end of her body so that the spermatophore lies against her genital opening or she picks up the sperm with her gonopods and deposits them in her genital atrium.

Single eggs are laid in Scutigeromorpha and Lithobiomorpha. Craterostimomorpha, Scolopendromorpha, and Geophilomorpha lay a group of 3–86 eggs that are protected by the mother, often in a hollow of a rotting log. Mothers hump their body around the egg cluster and the early hatchling instars in these three orders, ceasing feeding while brooding. Her grooming of the eggs seems to function to remove fungi. Eggs are camouflaged in soil, then abandoned in Scutigeromorpha and Lithobiomorpha.

Hatchlings have four pairs of legs in Scutigeromorpha, and six or seven pairs of legs in Lithobiomorpha; they are active from birth in those orders, and changes between subsequent instars are gradual. Hatchlings of Scolopendromorpha and Geophilomorpha have the adult number of legs. The first post-embryonic stages are incapable of hunting, and are brooded by the mother.

Breeding seasons vary for different species.

Conservation status

In general, centipede species have quite broad geographic distributions, and some are recorded from multiple continents. Many, however, are confined to narrower ranges, and some are known from single localities. A scolopendrid formerly collected in the Galápagos Islands may now be extinct. Introduced mammals and snakes on islands have decimated populations of some centipede species. Only one species (Scolopendra abnormis) is listed on the 2002 IUCN Red List; it is classified as Vulnerable.

Significance to humans

Centipedes have few uses to humans. Large Scolopendridae are used in the pet trade. Nearly all species are harmless to food crops and human goods (one species of geophilomorph is thought to feed on root crops). They have no role in causing or spreading diseases.

All centipedes are venomous, but most small species are incapable of piercing human skin or their bites are no worse than a bee sting. Bites by large Scolopendridae are painful, but pain and swelling pass after hours to days. There have been very few human deaths from centipede bites.

Species accounts

List of Species

Blind scolopender
Earth centipede
Tasmanian remarkable
Stone centipede
Scolopender
House centipede

Blind scolopender

Cryptops hortensis

order

Scolopendromorpha

family

Cryptopidae

taxonomy

Scolopendra hortensis Donovan, 1810, a garden in England.

other common names

None known.

physical characteristics

Length of head and body usually about 0.7 in (20 mm), but up to 1.2 in (30 mm); color pale brown to orange-brown; usually 17 antennal articles; eyes lacking; 21 pairs of trunk legs; last pair of legs with a saw-like row of teeth along the last two segments (5–8 on the tibia and 2–4 on the tarsus) before the claw; prefemur of last legs with a groove along ventral side.

distribution

Native to Europe and North Africa; widely distributed in Britain and Ireland; introduced to Scandinavia, Iceland, and the United States, where it has a wide distribution.

habitat

Woodland under bark and stones; common in gardens and hothouses in introduced parts of its range.

behavior

Quickly buries itself when disturbed; the anterior appendages push away soil, and the body wedged through loosened soil.

feeding ecology and diet

The last pair of legs has a prehensorial role. Their joints can strongly flex so that the saw-like row of spines grasps prey. The head is curved around and the maxillipede fangs are buried in the prey. Observed to kill flies, young caterpillars, and small harvestmen. Gut contents include spiders; other species of Cryptops have abundant earthworm remains in their guts.

reproductive biology

Courtship and sperm transfer have not been seen, but spermatophores are bean-shaped with a tough, multilayered wall as in Scolopendra. Another species, C. hyalinus, has a brood size of 7–9 eggs.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Earth centipede

Pachymerium ferrugineum

order

Geophilomorpha

family

Geophilidae

taxonomy

Pachymerium ferrugineum Koch, 1835, Europe.

other common names

German: Erdläufer.

physical characteristics

Length of head and trunk usually 1.2–1.3 in (30–35 mm), up to 1.9 in (50 mm); color reddish yellow, with head and maxillipede segment darker; eyes lacking; 43 trunk leg pairs in males, 43 or 45 in females; coxae of last leg pair not swollen, with many small coxal pores on its dorsal and ventral sides; last legs slender in female, swollen in male.

distribution

Throughout Europe, from Scandinavia to the Mediterranean, North Africa, Asia Minor and the Caucasus to Turkestan. Widely distributed in North America, where it is possibly introduced; also introduced to Japan, Taiwan, Hawaii, Juan Fernandez Island, and Mexico.

habitat

Common in coastal regions through most of its range. Inland occurrences are in grassland rather than woodland.

behavior

Like all geophilomorphs, adapted to burrowing in the soil by elongating and contracting the body. Can tolerate long periods of submergence in water.

feeding ecology and diet

Related Geophilomorpha have been observed to feed on worms, and in the laboratory, they accept small earthworms, soft insect larvae, adult fruitflies, and collembolans. Structure of the mandible suggests that semi-fluid food is swept into the mouth.

reproductive biology

Sexes distinguished externally by differences in the gonopods (two-segmented in male, stouter and single-segmented in female) and swollen last legs of male. Females lay between 20 and 55 eggs in a brood cavity (seen in moss or sand, likely also in soil); mother stops feeding for 40–50 days while guarding brood. Brooding occurs in summer. Mother usually eats brood when disturbed. Lifespan may be three years or more.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Tasmanian remarkable

Craterostigmus tasmanianus

order

Craterostigmomorpha

family

Craterostigmidae

taxonomy

Craterostigmus tasmanianus Pocock, 1902, near Hobart, Tasmania.

other common names

None known.

physical characteristics

Length of head and body up to 1.9 in (50 mm); color usually greenish brown with red-brown head; tapering antennae with 17–18 articles; one ocellus on each side of head shield; maxillipedes project in front of head shield; 15 pairs of trunk legs; long tergal plates subdivided in two (with a short pretergite), such that trunk appears to have 21 tergites; anogenital region enclosed in an elongate, ventrallyopening capsule with a mesh of openings for the coxal organs.

distribution

Throughout Tasmania. Records in New Zealand have been assigned to this species, but may be a distinct species.

habitat

Native forest and woodland, including rainforest, wet and dry eucalypt forest, subalpine woodland, and riparian and swamp forest; elevations from sea level to 4,265 ft (1,300 m). Favored microhabitats are in rotting logs, deep humus, and wet leaf litter.

behavior

Relatively slow moving. Like Scolopendromorpha and Geophilomorpha, it shows maternal care of the egg cluster and hatchlings, brooding in a hollow in a rotting log. Through most of its range, individuals are active year-round.

feeding ecology and diet

Natural prey unknown, but potential prey are amphipods, isopods, millipedes, fly larvae, beetles, collembolans, and mites. In captivity, has been observed to use the maxillipedes to dig termites out of crevices in wood, but not found in association with termite mounds in the wild.

reproductive biology

Sexes difficult to distinguish without examining testes or ovaries. Females found guarding egg clusters in September and guarding hatchlings in April. Number of eggs ranges from 44–77. Hatchlings emerge from the egg with 12 pairs of legs, and add the final three legs in the subsequent instar.

conservation status

Not listed by the IUCN; common through much of range, but vulnerable to forest clearing and burning in drier, eastern parts of Tasmania.

significance to humans

Isolated position of this species in centipede systematics gives it special scientific importance.

Stone centipede

Lithobius forficatus

order

Lithobiomorpha

family

Lithobiidea

taxonomy

Scolopendra forficata Linnaeus, 1758, Europe.

other common names

German: Braune Steinläufer, Gemeiner Steinkriecher.

physical characteristics

Length of head and body up to 1.2 in (30 mm); color chestnut brown; antenna with about 40 articles in mature specimens; cluster of ocelli (up to 40) on each side of head shield, with the posterior ocellus much larger than the others; 15 pairs of trunk legs; spiracles opening above legs on trunk segments 3, 5, 8, 10, 12, and 14; short trunk tergites 9, 11, and 13 with triangular projections at posterolateral corners; 5–9 elliptical coxal pores on each of legs 12–15.

distribution

Throughout Europe east to the Volga, Caucasus, Turkey, and North Africa. Widely distributed in North America, especially in the eastern United States, where it is likely an introduced species.

habitat

Usually found under stones, in rotting wood, or in moist leaf litter; common in woodland, grassland, and moorland as well as in gardens and greenhouses; broad elevational tolerance, from seashore to mountaintops. Moves from leaf litter in spring to logs and deep soil in summer and winter in parts of its range.

behavior

Has been observed to climb tree trunks and wander in the open at night. Cannibalism has been observed in the laboratory and field; gut contents include other L. forficatus. Stimulus for taking prey is tactile or chemical.

feeding ecology and diet

Carnivorous. Gut contents include earthworms and small arthropods such as collembolans, spiders, and mites. Has been seen in the field to catch woodlice, collembolans, worms, and slugs; in captivity, feeds on flies, beetle larvae, small moths, small spiders, spider eggs, and other small arthropods. Juveniles may be specialist collembolan feeders.

reproductive biology

Experiments suggest that the coxal organs on legs 12–15 emit sex-specific pheromones. Courtship ritual lasts a few hours, with tapping of last legs with antennae by both sexes, and male rocking body up and down. Male deposits spermatophore onto a 0.39 in (1 cm) wide web, then female moves over top of male and picks it up with her gonopods. Females lay single eggs nearly 0.039 in (1 mm) wide that are camouflaged with soil and abandoned; the eggs are held between a pair of stout spurs on each gonopod and the curved terminal claw of the gonopods.

In captivity, female seen to lay eggs 21 times over four months. Offspring hatch with seven leg pairs, with subsequent stages have 7, 8, 10, and 12 pairs, then post-larval (15-legged) stages. Life span may be 5–6 years.

conservation status

Not listed by the IUCN.

significance to humans

May be a predator on apple maggot pupae in apple orchards; preys on the symphylan Scutigerella immaculata, a greenhouse pest.

Scolopender

Scolopendra morsitans

order

Scolopendromorpha

family

Scolopendridae

taxonomy

Scolopendra morsitans Linnaeus, 1758, southern Europe.

other common names

German: Skolopender, Riesenläufer.

physical characteristics

Length of head and body up to 5.1 in (130 mm); color of head shield variable, trunk tergites yellow or brown with a dark band along posterior margin; cluster of four ocelli on each side of head shield; 17–23 (usually 18–21) antennal articles; maxillipedes with a pair of tooth plates, each usually with five teeth; 21 pairs of trunk legs; tracheae open to triangular spiracles above legs on segments 3, 5, 8, 10, 12, 14, 16, 18, and 20; pair of median sulci on trunk tergites 2–20; prefemur of last leg with five rows of small spines (two rows on dorsal side, three rows of usually three spines on ventral side); prefemur extended as a process with 2–6 spines on its apex.

distribution

Very widely distributed through the tropics and warm parts of the temperate zone, including Central America and the Caribbean, much of Africa, Madagascar, South and East Asia, and Australia; a few records in tropical South America.

habitat

Variable, from desert to rainforest.

behavior

Relatively fast runner, able to quickly penetrate litter when disturbed. The related S. cingulata burrows under stones and stays in a series of linked chambers for a few days. Contacts between individuals involve a ritual in which the animals grip each other with their last leg pair. Active at the surface throughout the year in at least parts of range.

feeding ecology and diet

Like most large scolopendrids, hunting is mostly nocturnal, the day spent in leaf litter, or under logs or bark. Gut contents show arthropod prey, including spiders, mites, centipedes, flies, beetles, ants, and termites. In the laboratory, reported to take frogs, small toads, and cockroaches.

reproductive biology

As in all Scolopendromorpha, gonopods are lacking but sexes are distinguished externally by conical penis in male. Males have flattened dorsal side of some segments on last legs. Females tend to be larger. Males deposit a bean-shaped spermatophore 0.01 in (2.5 mm) long through the penis onto a web. The mother's brood chamber is hollowed out in the soil under a stone, with 28–86 elliptical, greenish yellow eggs being laid. In parts of range (Nigeria), reaches maturity within a year, with two generations per year.

conservation status

Not listed by the IUCN.

significance to humans

None known.

House centipede

Scutigera coleoptrata

order

Scutigeromorpha

family

Scutigeridae

taxonomy

Scolopendra coleoptrata Linnaeus, 1758, Spain.

other common names

German: Spinnenassel.

physical characteristics

Length of head and trunk up to 1.2 in (30 mm); color yellow or brown with three purple or blue bands along the length of the tergal plates; large compound eyes on each side of head; antenna divided into 500–600 annulations; spiracles opening as a slit on the rear margin of each of seven large tergal plates; 15 pairs of trunk legs, with tarsal segment of each flagellum divided into 250–300 annulations.

distribution

Native to the Mediterranean region (southern Europe and North Africa) and the Near East; introduced and widely distributed in North America and South Africa; limited distribution where introduced in Britain, northern Europe, Australia, Argentina, Uruguay, tropical Africa, and Taiwan.

habitat

Woodland, under pieces of wood and in litter; also found in caves; in introduced parts of its range, usually found in damp places in houses and woodpiles.

behavior

Cannibalism has been observed. In the laboratory, specimens remain at the litter surface day and night, quickly scurrying for cover when disturbed. They are immobile while awaiting prey; contact seems necessary to recognize prey, which is grabbed immediately. Can run at 16 in (40 cm) per second.

feeding ecology and diet

In the lab, only live animals are taken. Prey includes many kinds of arthropods (flies, cockroaches, moths, spiders); generally eating only the soft parts. The anterior legs snare prey, keep it from escaping, and can hold on to captured flies while another fly is eaten.

reproductive biology

Both sexes are distinguished externally by their gonopods; unique in having two pairs of male gonopods. Courtship involves partners forming a circle, tapping each other with their antennae; male rocks body up and down, and deposits a lemon-shaped spermatophore; male guides female to spermatophore, from which she removes sperm. Eggs oval, 0.05 in (1.25 mm) long. Female holds egg between gonopods, wipes it with soil, and deposits it in a soil crevice. Usually about four eggs laid per day over a breeding season of about two months (May–June in southern France). Eggs hatch in 30–38 days. Hatchlings have four pairs of legs, with subsequent stages having 5, 7, 9, 11, and 13 pairs, then five post-larval (15-legged) stages. Individuals have lived nearly three years in captivity.

conservation status

Not threatened.

significance to humans

Preys on domestic flies and cockroaches.

Resources

Books

Lewis, J. G. E. The Biology of Centipedes. Cambridge, U.K.: Cambridge University Press, 1981.

Minelli, Alessandro. "Chilopoda." In Microscopic Anatomy of Invertebrates. Volume 12, Onychophora, Chilopoda, and Lesser Protostomata. New York: Wiley-Liss, 1993.