Diptera (Mosquitoes, Midges, and Flies)
Diptera
(Mosquitoes, midges, and flies)
Class Insecta
Order Diptera
Number of families 188
Evolution and systematics
Permotipula patricia from the Upper Triassic of the Mesozoic period from Australia, about 225 million years ago, is the earliest known fossil of a true fly. Since that time, flies have diversified to become one of the four largest orders of insects with about 124,000 species described. It is estimated that an equal number of species, mostly from tropical forests, still await description.
Diptera or true flies are the closest relatives to the Mecoptera or scorpionflies within the Panorpoid-complex (including butterflies and moths, scorpionflies, and fleas), with which they share numerous wing venation characters. Flies are distinguished from other insects by several derived characters, the more important of which are: metathoracic wings transformed into clublike halteres, metathorax reduced in size, labium modified as a labellum, and larval spiracles lacking a closing apparatus.
The order Diptera is divided into two suborders, Nematocera and Brachycera. Nematocera includes generally small, delicate insects with long antennae, regarded as more primitive flies, such as mosquitoes, crane flies, midges, punkies, and no-see-ums. Brachycera includes more specialized, compact, robust flies with short antennae. In older classifications, two divisions were recognized within Brachycera: Orthorrhapha and Cyclorrhapha. The Orthorrhapha includes brachyceran flies with free pupae (lacking a puparium) and larvae with incomplete head capsule, such as horse flies and robber flies, and the Cyclorrhapha comprises brachyceran flies with pupae enclosed in the hardened skin of the last larval instar (called puparium) and larvae without head capsule. The Cyclorrhapha are further divided into two groups based on the presence or absence of the ptilinum and associated fissure on the head. The ptilinum is a sac that is everted only once during the emergence of the adult fly to assist in breaking free of the puparium. The Aschiza (flower flies and coffin flies) lack the ptilinum, whereas it is present in the Schizophora. Schizophora in turn comprises a group of flies, the Calypteratae (including house, bottle and flesh flies), with basal lobes in the wings called calypters, and a second group without such lobes, the Acalypteratae (including fruit, vinegar, and oil flies).
These traditional groupings of Diptera have been critically reexamined in recent decades, and many of the categories such as the Nematocera, Orthorrhapha, and Aschiza are not considered natural groups. Instead, these categories consist of a collection of basal lineages from which some natural groups (Brachycera, Cyclorrhapha, and Schizophora, respectively) arose. No consensus has been reached to date on a natural classification for the order.
Physical characteristics
Adults have a mobile head, with large compound eyes that can be contiguous (holoptic condition, found usually in males) or separated (dichoptic condition, most commonly encountered in females) on top. The antennae have six or more segments in nematoceran flies, and five or fewer in brachyceran flies. Mouthparts are adapted for sucking and form a proboscis or rostrum. In predatory species, the mandibles form a pair of piercing stylets, and in cyclorrhaphan flies the labial palps form the labella, membranous sponge-like apical lobes traversed by sclerotized canals called pseudotracheae, through which liquids ascend by capillary action. The major morphological feature that distinguishes flies from other insects is the presence of only one pair of functional wings, hence their scientific name (di = two, pteron = wing). The mesothorax has become greatly enlarged to contain the powerful flight muscles, and the pro- and metathorax are reduced. The hind wings are modified into halteres, which are small, club-like structures that function as balancing organs during flight. A few other groups of insects have also attained a similar two-winged form, such as males of scale insects (Coccoidea, Hemiptera), and a few flies have lost their wings and halteres as an adaptation to a parasitic life style (e.g., louse-fly families Nycteribiidae and Hypoboscidae) or habitats such as tidal pools (e.g., the midge Pontomyia in the Indopacific), snow fields (e.g., the crane fly Chionea in Europe), islands (e.g., the crane fly Limonia hardyana and the dolichopodid fly Campsicnemus from Hawaii), or coffins (e.g., the phorid fly Conicera). However, those flies are still recognizable by the structure of their mouthparts, greatly enlarged mesothorax, and legs.
There is a large diversity in leg shape and structure, but all species in this order have five tarsomeres (distal segments), which are used as tactile organs. Legs can be adapted as raptorial organs in predatory forms (e.g., the fore legs of some ceratopogonids, empidids, and ephydrids) or for holding onto the female during copulation, as organs of sexual or combative display (e.g., the ornamented tarsi of some African dolichopodid flies), or as grasping organs in ectoparasites, and can bear combs of setae and brushes of hairs for grooming. The abdomen of flies has a basic number of 11 segments, the last one called the proctiger, represented by only the caudal appendages or cerci and the anus. In nematoceran and orthorrhaphan flies, the abdomen is usually longer and slender, whereas it tends to be robust in the Cyclorrhapha. The male aedeagus or intromitent organ is found on the underside between abdominal segments 9 and 10, and the female genital opening is between segments 8 and 9. Female flies do not have an ovipositor formed by valves; instead, in the more advanced flies, the terminal segments of the abdomen, from 5 or 6 to the tip, form a "functional ovipositor" in the shape of a tapered telescopic tube. The apical portion of the male abdomen is often flexed—folded ventrally, laterally, or dorsally—and the genitalia is usually twisted 90° to 360° as an adaptation for mating and storing the genitalia when not in use.
Larvae are usually elongated and subcylindrical or fusiform, and often have transverse swollen areas called creeping welts that usually bear a transverse series of microspinules on the ventral surfaces—or on both the ventral and dorsal surfaces—of the first seven abdominal segments. Larvae always lack external wing pads and legs, although some may have fleshy tubercles called prolegs on the prothorax and some abdominal segments. Nematoceran larvae have a sclerotized head capsule and mouthparts that move in a horizontal plane. In Brachyceran larvae, also called maggots, the mandibles move in a vertical plane, the head capsule is reduced (in orthorrhaphan flies) or absent (in cyclorrhaphan flies), and the head possesses an internal cephalo-pharyngeal endoskeleton. Larvae differ in the number of spiracles or openings for their respiratory system. They may be apneustic (without openings); amphipneustic (with an anterior and a posterior pair of spiracles); or metapneustic (with only the posterior pair of spiracles). Aquatic larvae spiracles may be situated at the tip of projections of the body called siphons, which allow them to reach the atmosphere (e.g., in the rattailed maggot, the larva of an Eristalis syrphid fly, which lives in the bottom of bodies of oxygen-poor water and breaths through a very long siphon, the tail) or pierce underwater aircontaining plant tissues (e.g., several mosquito larvae with sawlike siphons).
Diptera pupae have nonfunctional mandibles and one pair of wing pads. The appendages may be free from the body (as in Nematocera) or glued to the body (as in Orthorrhapha brachyceran flies), and the pupa may be free or concealed inside the puparium (as in Cyclorrhapha brachyceran flies).
Distribution
Flies are found on all continents including Antarctica, where two species of midges occur. Most families reach higher species richness in the tropics than in the more temperate areas, although Mycetophilidae, Chironomidae, and Empididae are most diverse at higher latitudes. Some species are very restricted in distribution, such as the wood-boring flies of the family Panthophthalmidae that occur only in Brazilian forests, the wingless fly Mormotomyia hirsuta, which is known only from a single fissure in a rock in Kenya where it feeds on bat dung, and the tabanid Thriambeutes mesembrinoides from the Usambara Mountains in Tanganyika.
Habitat
Larvae occur in aquatic, semiaquatic, and moist terrestrial environments, as endoparasites of other animals or as miners within plant tissues, but because their cuticle is soft and susceptible to desiccation, only a few live in dry environments.
Larvae of some shore flies (family Ephydridae) live in unusual habitats that would be lethal for other insects, such as hot springs and geysers where the water temperature exceeds 112°F (44.4°C) (Ephydra brucei), pools of crude oil (Helaeomyia petrolei), and ponds with very high concentrations of salt (the brine fly Ephydra cinera). Some bombyliid larvae live inside the nests of various bees, ants, and wasps, on which brood they feed.
The pupa normally occupies the same habitat as the larva. Pupation of most of the fully aquatic species occurs under-water, while semiaquatic species may pupate above water. The pupa may swim to the surface before the adult emerges, or it may remain on the bottom.
Adults are usually terrestrial, active in the daytime, and almost always free-living, the exception being the ectoparasitic adults of the louse-flies (families Hippoboscidae, Streblidae, and Nycteribiidae).
Behavior
Aggregations occur in many flies. Many Bibionidae and Empididae species as well as numerous nematoceran flies form aerial swarms, in which adults—usually males—hover together around some fixed object, such as a tree or bush, a hill top, a rock on a stream, a patch of sunlight in a forest, a building, or a highway (e.g., the lovebug, a bibionid fly that forms mating swarms on roads from Central America to the southern United States). These swarms usually allow males to be more conspicuous to their prospective mates. Other adults form sedentary aggregations for the purpose of mating or for seeking shelter or warmth, such as on roofs, or as the result of a mass emergence. Larvae can also form aggregations, such as leatherjackets and bibionids in the soil and the armyworms
(Sciara militaris), which can be seen marching in long columns across European forests.
Mimicry is known in several flies that imitate ants (e.g., Sepsisoma, richardiid flies that mimic Camponotus ants; Microdon mutabilis, syrphid flies that imitate Formica lemani and Myrmica scabrinodis); bees and wasps (e.g., several conopid and tephritid fruit flies species that mimic vespid wasps); bumblebees (e.g., Laphria asilids that mimic Bombus species); and jumping spiders (e.g., fruit flies with banded wings and/or spotted abdomens). The mimicry can be in shape as well as behavior, either as a strategy to deceive the model in order to feed or lay eggs on its brood, or to deceive potential predators.
Feeding ecology and diet
Larvae are phytophagous (feeding on leaves, fruits, or roots of plants), filter organic matter, or are scrapers of algae, predators, parasitoids and saprophagous feeders of decaying organic matter including vegetables, dead animals, or dung. Endoparasitic larvae include those in the family Tachinidae, which parasitize other insects, particularly centipedes and spiders; those in the family Pipunculidae, which parasitize the larvae of cicadas and leafhoppers; and some species of bee flies (family Bombyliidae), which develop in the eggs or larvae of bees and wasps, other flies, beetles, and butterflies.
Adults typically consume liquid food such as nectar and other plant exudates or decomposing organic matter, or they prey on other insects or mollusks; adults of some species feed on little or nothing at all. Females of some groups may take blood meals from vertebrates (e.g., the "biting" mosquitoes, no-see-ums, black flies, and horse flies) as a prerequisite to oviposition.
Reproductive biology
Flies undergo complete metamorphosis, passing usually through four life stages: egg, larva, pupa, and adult. The basic number of larval instars is 4 to 9 for the lower Diptera (Nematocera), and only three in many Cyclorrhapha, as the fourth larval stage develops within the puparium. The length of the egg stage is often brief, encompassing a few days or weeks, and that of the larval stage is variable, ranging from a few days in larvae feeding on short-term resources (such as rotting meat) to more than two years in some larvae that develop in cold and moist habitats.
Mating in flies is often preceded by an initial courtship in which the male or both sexes perform a chain of actions involving body movements or vibrations of the wings. In some dance-flies (family Empididae), males offer a nuptial gift to the female as part of the courtship, such as an insect wrapped up in silk, or just a hollow balloon of silk. Mating usually starts with an initial coupling position of both sexes facing in the same direction, and ends in a final mating position with male and female facing in opposite directions, in a tail-to-tail orientation. Some species are parthenogenetic (e.g., some Drosophila, Lonchoptera, Sciara, and Diaphorus flies).
Egg laying is related to the habitat of the larvae. Fruit fly females have a long needle-like ovipositor with which they pierce the skin of the fruit in which the larvae live and feed; parasitic flies show an extraordinary array of strategies to get eggs into their hosts, including laying them on the host's surface, inserting them into the host with a piercing ovipositor, pasting them close or onto the host's nest, hiding them among the host's food, or laying them on another animal that will eventually come in contact with the host, such as a tick or mite. Flies with aquatic larvae oviposit on the water or on rocks or vegetation overlaying the water, and eggs can be laid singly or in the form of rafts.
Conservation status
Several flies are threatened not by direct exploitation but by loss or degradation of their habitats; they are at risk because their ecosystems are at risk. The IUCN Red List includes seven species from this order; three as Extinct, two as Endangered, one as Critically Endangered, and one as Vulnerable. The three Extinct species are the Volutine stoneyian tabanid fly, Stonemyia volutina (Tabanidae), from the continental United States; the Ko'okay spurwing long-legged fly, Campsicnemus mirabilis (family Dolichopodidae), from the Hawaiian Islands; and Lanai pomace fly, Drosophila lanaiensis (Drosophilidae), also from Hawaii. The sugarfoot moth fly, Nemapalpus nearcticus (family Psychodidae), from the United States, and the giant torrent midge, Edwardsina gigantea (family Blepharoceridae), from Australia, are Endangered. The Tasmanian torrent midge, Edwardsina tasmaniensis (family Blepharoceridae), is Critically Endangered due to the establishment of a hydroelectric dam in the Launceston Cataract Gorge at the Dennison River in Australia. Finally, Belkin's dune tabanid fly, Brennania belkini (Tabanidae), from Mexico and United States, is considered Vulnerable because of the progressive destruction of its habitat by urban development.
Although not listed by the IUCN, the flower-loving fly, Rhaphiomidas terminatus (family Apioceridae), from California, is at risk of extinction. Rhaphiomidas terminatus consists of two subspecies, the Delhi sands flower-loving fly, R. terminatus abdominalis, and the El Segundo flower-loving fly, R. terminatus terminatus. The latter, confined to the El Segundo sand dunes and portions of the sandy alluvial plain of the Los Angeles River—the last remains of which were eliminated by construction for the Los Angeles International Airport in the 1960s—was thought to be extinct but has recently been rediscovered. The Delhi sands flower-loving fly is a rare endemic subspecies restricted to the Delhi series of sand dunes, 98% of which have been converted to residential, agriculture, and commercial uses. The subspecies is listed as Endangered by the United States Fish and Wildlife Service.
Significance to humans
Flies are the most important arthropod vectors of disease in humans and other animals. For example, malaria is believed to have killed more human beings than any other known disease and is still a major cause of illness in many tropical countries. Also, diseases transmitted to humans and livestock by tsetse flies were the main obstacle to European colonization of North Africa. Deer or horse flies can transmit bacterial diseases such as tularemia and anthrax, filariasis (via the Loa Loa worm), and trypanosomiasis (causing surra in caribou, horses, and camels). Mosquitoes are vectors of filariasis (elephantiasis), malaria (caused by four species of the protozoan Plasmodium), and viruses including yellow fever and dengue fever; black flies can transmit onchocercosis (via worms); tsetse flies are vectors of trypanosomiasis (causing the fatal disease nagana in cattle and sleeping sickness in humans); and sand flies are vectors of leishmaniasis (via the Leishmania protozoan).
In addition to serving as vectors for diseases, flies can cause health problems themselves. Three main dipteran families— Oestridae (bot flies), Sarcophagidae (flesh flies), and Calliphoridae (bottle flies) cause economically important myiasis in livestock and also occasionally in humans. Myiasis is the infestation of live vertebrate animals by dipterous larvae, which at least for a certain period feed on the host's dead or living tissue, liquid body substances, or ingested food.
Still others are nuisance pests or carry filth, such as the eye gnats (genus Hippelates, family Chloropidae) and face flies (Musca autumnalis, family Muscidae), attracted to the secretions of the eyes of vertebrates; or the house flies (Musca domestica, family Muscidae), little-house flies (Fannia, family Muscidae), and latrine flies (Chrysomyia, family Calliphoridae), which breed in excrement and garbage.
Fruit flies (family Tephritidae) are among the most destructive agricultural pests in the world, eating their way through citrus crops and other fruit and vegetable crops at an alarming rate and forcing food and agriculture agencies to spend millions of dollars on control and management measures. Other agricultural pests include the gall gnats (family Cecidomyiidae), leaf miner flies (family Agromyzidae), and root miner flies (family Anthomyiidae).
Besides their essential roles in our ecosystems, including serving as food items for numerous animals and as pollinators, flies are of some direct benefit to humans. Some are important as biological control agents of weeds and other insects; as indicators of water quality (e.g., midge larvae known as blood worms are indicators of polluted environments); as experimental animals (e.g., much of our knowledge of animal genetics and development has been acquired using the fruit fly, Drosophila melanogaster as an experimental subject); and in forensic investigations to establish the time of death, whether the corpse has been moved after death, and the cause of death (e.g., several larvae of families Trichoceridae, Stratiomyidae, Phoridae, Phanidae, Muscidae, Calliphoridae, Sarcophagidae, and others feed on carrion and flesh in different degrees of decomposition, in different situations, and at different times of the year).
Species accounts
List of Species
Dasypogon diademaNew World primary screwworm
Yellow fever mosquito
Cyrtodiopsis dalmanni
Petroleum fly
Tsetse fly
New Zealand glowworm
Spider bat fly
Horse bot fly
Fire ant decapitating fly
Dawson River black fly
Chevroned hover fly
Big black horse fly
Mediterranean fruit fly
European marsh crane fly
No common name
Dasypogon diadema
family
Asilidae
taxonomy
Asilus diadema Fabricius, 1781, Italy.
other common names
None known.
physical characteristics
Adults are large (about 0.6 in [15 mm]) and sexually dimorphic; males have black abdomen and blackish wings, and females have black abdomen with red markings and brownish wings and are usually larger. Eggs are white, long, oval, and are laid in groups of 1–6 in cocoons made with sand grains glued together and covered inside with a silky lining. Larvae are white to yellowish, elongate, cylindrical, and tapering at each end. Pupae have transverse rows of elongate spines or bristles arising dorsolaterally, and abdominal segment 9 has 1–4 pairs of strongly sclerotized terminal caudal hooks.
distribution
Central region of Mediterranean Europe.
habitat
Open, dry, and sandy areas such as steppes, partly eroded hill slopes, sandy hollows, weedy grass plots, dunes, dry meadows, pastures, and olive groves.
behavior
Males continuously look for females. Females are more territorial, remaining longer at their foraging positions perched upwards on stems, or sometimes on the ground. They only fly if they see potential prey or if males disturb them. During periods of inactivity, they hang on stems of flowers and grasses or under leaves.
feeding ecology and diet
Larvae feed on larvae of scarab beetles (order Coleoptera, family Scarabeidae), and adults mostly on hymenopterans, including honey bees (Apis mellifera). With their long, thin legs, the strong spur at the apex of the foretibiae, and long proboscis, they are well adapted for subduing wasps and bees without being stung. After catching a prey in flight, they look for an appropriate perching site before sucking the prey's contents.
reproductive biology
Mating is initiated after a short struggle, when the male grasps the female's ovipositor with his genital claspers. Final mating position is end-to-end. The female then flies with the male in copula looking for a suitable place to land. After mating, the female lays the eggs in clutches in the soil, protected inside sand cocoons. The four larval instars and the pupa live in the soil.
conservation status
Not threatened.
significance to humans
None known.
New World primary screwworm
Cochliomyia hominivorax
family
Calliphoridae
taxonomy
Lucilia hominivorax Coquerel, 1858, French Guiana.
other common names
English: American primary screwworm; Spanish: Gusano barrenador del ganado.
physical characteristics
Adults are 0.4–0.6 in (10–15 mm) long, metallic blue to bluish green, with three longitudinal black stripes on the thorax. Face and eyes are orange-brown; palps are short and threadlike, and antennae are plumose to their tips. The larvae are whitish, about 0.4–0.5 mm (10–12 in) long, and have large posterior spiracles, each with three straight slitlike apertures surrounded in part by a prominent dark-pigmented peritreme. They have a ring of spinules on each segment, which gives them the appearance of a screw.
distribution
Native to tropical and subtropical areas of the Americas. The screwworm has been eradicated from the southern United States and Mexico and most of Central America. There is a seasonal spread of the screwworm into the temperate regions of Argentina, Uruguay, and Paraguay during spring and summer, and it is occasionally reported from Chile and southern Argentina from imported animals. It was imported to Libya in North Africa around 1988 and eradicated three years later.
habitat
Tropical and subtropical areas; cannot overwinter where soil freezes.
behavior
Mature larvae are negatively phototropic (they move away from light), and this behavior facilitates burrowing in the soil to pupate. Adult flies disperse to find mates and oviposition sites. In tropical environments, females tend to disperse only 6.2–12.4 mi (10–20 km) when there is a high density of animals; in arid environments with lower densities of animals, screwworm flies have traveled as far as 186 mi (300 km). In more arid areas, screwworm flies travel along water courses, and in mountainous areas, along the course of valleys, where the climate is warmer and moisture and animal density higher.
feeding ecology and diet
Larvae are obligate ectoparasites (external parasites that cannot complete their cycle outside of their host) of mammals and will infest warm-blooded livestock, wildlife, and humans; they are unable to breed in carrion. A cut, abrasion, or other wound in the skin is required for the larvae to invade the host tissue, where they feed on the living tissue. Adults imbibe water and nectar and fluids of exposed wounds.
reproductive biology
Individual females lay batches of 200–300 eggs in compact masses on the skin at the edges of fresh wounds or areas where there is a bloody or mucous discharge. Even wounds the size of a tick bite are sufficient to attract oviposition. The eggs hatch in 14–18 hours. Within a day of hatching, the maggots start to feed, burrowing into the living tissue, where they bunch together to feed with their posterior spiracles exposed. In 5–9 days, larvae are fully developed and leave the host to pupate in the soil for about seven days. After 3–5 days of emergence, adult flies are ready to mate. Male screwworm flies will mate several times, while females usually mate only once. Under ideal conditions, the life cycle is completed in 24 days.
conservation status
Not threatened.
significance to humans
The screwworm is an economically important pest of domestic cattle. Wounds infested by screwworm larvae become increasingly attractive to fly species whose larvae breed on dead organic material, and also to gravid females of the primary screwworm, thus making the syndrome self-perpetuating in endemic areas, where the result is usually the death of the host.
Yellow fever mosquito
Aedes aegypti
family
Culicidae
taxonomy
Culex aegypti Linnaeus, 1762, Egypt.
other common names
None known.
physical characteristics
Small in comparison to other mosquitoes, between 0.1–0.15 in (3–4 mm) long, black with a white lyre-shaped patch of scales
on its thorax and white rings on the legs; wings translucent and bordered with scales. The eggs are white when freshly laid but soon turn black.
distribution
Originally from Africa but has spread by human activity to all tropical and subtropical regions of the world between 45°N and 35°S latitudes.
habitat
The yellow fever mosquito is peridomestic, breeding in or near human dwellings in hot, humid areas, and is particularly abundant in towns and cities. Females are early morning or late afternoon feeders but can take a blood meal at night under artificial illumination. Human blood is favored over that of other animals, with preference for the ankle area. Adults usually rest in dark or dimly lit closets, cabinets, or cupboards during the day. Larvae are aquatic.
behavior
At rest, the insect turns up its hind legs in a curved fashion and usually cleans them by rubbing one against the other, or crosses them and alternately raises and lowers them.
feeding ecology and diet
Males of mosquitoes do not bite humans or animals of any species; they live on fruit juices. By contrast, the females need a blood meal in order to induce the maturation of their eggs. The larvae feed on plankton they filter from the water.
reproductive biology
Females lay eggs singly on damp surfaces or clean water held in small containers such as old automobile tires, drums, jars, natural water-retaining cavities in plants, and tree holes. The eggs can resist desiccation for up to one year, and they will hatch when flooded by water. After a few weeks from hatching, or even 4–10 days if it is warm enough, the larvae reach the pupa stage, which is usually of short duration. Pupae rise to the surface of the water, where the top of the pupal case opens and the new adult emerges. The species is summer-active in higher latitudes and active all year in tropical areas. Adults are killed by temperatures below freezing and do not survive well at temperatures below 41°F (5°C). On average, females live up to a month, but males die sooner.
conservation status
Not threatened.
significance to humans
Aedes aegypti is the most important domestic vector of the viruses that cause human dengue and urban yellow fever, and for the chikungunya virus in Asia.
No common name
Cyrtodiopsis dalmanni
family
Diopsidae
taxonomy
Diopsis dalmanni Wiedemann, 1830, Java, Indonesia.
other common names
None known.
physical characteristics
The most striking characteristic of flies in this family is the position of the eyes on the tip of lateral stalks, which gives them the common name "stalk-eyed flies." In males of Cyrtodiopsisdalmanni, the length from one compound eye to the other is nearly the length of the body; females have shorter eye-stalks.
distribution
Widespread in Southeast Asia.
habitat
Found among forest-floor detritus in damp and well-shaded areas near streams in primary or secondary forests.
behavior
The long and rigid eye-stalks are used for improved visual orientation and, in males, for sexual competition. The forelegs, adapted for gripping, are used in combats with rivals. The extreme eye-stalk structure requires special foreleg movements to clean the eyes.
feeding ecology and diet
Larvae feed on plants. Feeding habits of the adults are still unknown.
reproductive biology
Adults stop grazing in the evening, and males stake out rootlets dangling from stream banks. On a disputed rootlet, males face off eye to eye, and the one with the shorter eye span backs down. Several females are found together with a long stalkeyed male and show continuous sexual receptivity and high rates of multiple mating. Males with exaggerated eye spans can mate with as many as 24 partners in half an hour. After emergence from the puparium, stalk-eyed flies go through a pumping process for about 15 minutes to unfold the eye stalks to their full length simultaneously with the wings.
conservation status
Not threatened.
significance to humans
None known.
Petroleum fly
Helaeomyia petrolei
family
Ephydridae
taxonomy
Psilopa petrolei Coquillet, 1899, California.
other common names
English: Oil fly.
physical characteristics
Adults are small (0.08 in [2 mm]), and their bodies are black and pruinose except cheeks and sides of face, which are grayish. Eyes are hairy and wings are hyaline and tinged with gray on their costal (anterior) half. Larvae are elongate, reaching a length of 0.3–0.4 in (7–10 mm). They breathe through spiracles on their posterior end, which are surrounded by four supporting fans of setae; the fans rest upon the surface of the oil and keep the spiracles above the surface.
distribution
California oilfields.
habitat
This is the only insect known from which larvae develop in seepages of crude oil.
behavior
Larvae swim slowly, usually near or on the surface of the oil, although they can submerge for a considerable length of time. Adults remain near petroleum pools, hiding in the cracks in the soil, flying about and over the pools, and landing on the margin or on some projecting stone or stick within the pool. They can walk on the surface of the oil as long as no body part other than the tarsi comes in contact with the oil.
feeding ecology and diet
The larvae feed on dead insects that have become trapped in the oil pools.
reproductive biology
Mating behavior and oviposition are still undescribed. When ready to pupate, the larva leaves the oil and pupates on grass stems on the margins of the pool.
conservation status
Not threatened.
significance to humans
Crude oil is usually regarded as a very effective insecticide. Thus, petroleum flies are of interest to biotechnologists because they can provide information regarding the ability of organisms to resist the toxic effects of aromatic and petroleum compounds.
Tsetse fly
Glossina palpalis
family
Glossinidae
taxonomy
Nemorhina palpalis Robineau-Desvoidy, 1830, Congo River.
other common names
None known.
physical characteristics
Adults are yellowish to brown, with a forward-projecting, piercing proboscis and a hatchet-shaped cell in the center of each wing. The arista arising from the third antennal segment has branched setae. Both sexes have dichoptic eyes. Larvae breathe through a pair of posterior spiracles and in the third stage via a pair of lateral lobes, which contain three air chambers and open through numerous spiracles.
distribution
Western Africa.
habitat
Local patches of dense vegetation along banks of rivers and lakes in arid terrain, and also in dense, wet, heavily forested equatorial rainforest.
behavior
Larvae show negative phototaxis (avoiding light) and are positively thigmotactic (seeking contact with surfaces).
feeding ecology and diet
Adults feed on the blood of any vertebrate they encounter, including reptiles—especially monitor lizards and crocodiles— birds, and mammals. They are not responsive to the conventional vertebrate host odors that other tsetse flies respond to. This species generally feeds while inside dense humid forest habitats, where trailing hosts by sight is easier than by olfaction.
reproductive biology
Female tsetse flies reproduce by adenotrophic viviparity, which involves the retention of a single egg that develops to the third larval stage before being deposited. The egg within the uterus hatches in 3–4 days, giving rise to the first-stage larva. The larva feeds from secretions of a pair of uterine glands from the mother. Just before depositing her larvae at the third instar, the adult female actually weighs less than her offspring. The larvae are deposited on the soil and burrow down, where they pupate for 4–5 weeks. The young adult emerges from the puparium using its ptilinum, which it also uses to move up through the soil. Having emerged, both sexes seek a host to gain a blood meal. Males are not fully fertile until several days after emergence, and females are able to mate two to three days after emergence. The first larval offspring is deposited about 9–12 days after the female emerges. Due to the length of development, tsetse flies are relatively long-lived, up to 14 weeks for females, with males having shorter lives of around 6 weeks. Hence the rate of reproduction is extremely slow compared to other dipteran species.
conservation status
Not threatened.
significance to humans
This species is an important vector of West African trypanosomiasis via the protozoan Trypanosoma brucei gambiense, which causes nagana in horses and cattle and sleeping sickness in humans.
New Zealand glowworm
Arachnocampa luminosa
family
Keroplatidae
taxonomy
Bolitophila luminosa Skuse, 1891, New Zealand.
other common names
English: New Zealand fungus gnat, glowing spider bug; Maori: Titiwai.
physical characteristics
All stages, except for the eggs, glow. The eggs are small and white and turn brown before larvae emerge. Eggs are coated with a sticky substance and adhere to the substrate. Larvae go through five instars and reach a body length of 1.2–1.6 in (30–40 mm). They are brown but with transparent skin, allowing bluish green light to shine through. Adults are slightly larger than a mosquito, about 0.50 in (15 mm) in length.
distribution
New Zealand.
habitat
Damp, sheltered areas with hanging surfaces, dark for a good portion of the day and protected from winds, such as caves; usually associated with streams.
behavior
During the day larvae hide in crevices, and during the night they enter their silk tubes and hunt. Bioluminescence is used to attract food in larvae and mates in adults; the hungrier a larvae is, the brighter it glows. If no male is waiting on a female's pupa when the female is ready to emerge, the female will glow brighter and will flash its lights on and off. The flight of adults is slow, and their habits are mostly crepuscular or nocturnal. They are often found on low vegetation, under overhanging rocks and trunks, and along banks of streams.
feeding ecology and diet
Glowworm larvae are voracious hunters with large mandibles. They spin a delicate web of horizontal silk tubes from special labial glands in their heads. This web is attached to rocks and branches and suspended from the tubes; they hang from silk threads covered with globules of sticky mucous that can reach 20 in (50 cm). Insects that are attracted to the light of the larvae become caught in the sticky mucous of these "fishing lines." Vibrations are sent up the line and sensed by the larva, which then begins to swallow the line. Certain chemicals within the mucous paralyze the prey, which is finally bitten and killed by the larva. New Zealand glowworms can be cannibalistic, with the larvae often eating other larvae or even adults that happen to fly into the fishing lines. They also feed on mosquitoes, moths, stoneflies, sand flies, caddisflies, midges, ants, spiders, millipedes, and even snails. Adults have reduced mouthparts and do not feed.
reproductive biology
Females ready to hatch begin to emit light while still inside the pupa. This attracts males, which land on the pupa and fight with each other in an attempt to dislodge each other from the pupa's surface. This ensures that only the strongest males mate with the females as soon as they hatch. Upon emerging from the pupa, males live for three to five days and females for one or two days. Females lay the eggs one at a time in clusters of 30–40, usually on muddy banks, and can lay as many as four clusters. The eggs hatch after three weeks, and the larvae emerge emitting light and immediately begin to build their homes. The larval stage lasts roughly 6–12 months. When it is time to pupate, the larva arranges its sticky fishing lines into a protective, circular barrier and then hangs in the middle of this circle. Pupation takes about 12 days.
conservation status
Not threatened.
significance to humans
Caves with gatherings of glowworms constitute a tourist attraction.
Spider bat fly
Basilia falcozi
family
Nycteribiidae
taxonomy
Nycteribia falcozi Musgrave, 1925, Australia.
other common names
None known.
physical characteristics
Adults lack wings and their body is compressed dorsoventrally, so that head and legs arise from the dorsal surface of the thorax,
giving them a spiderlike appearance. They have long legs with strong claws. The pupae are shining black and flattened.
distribution
Australia.
habitat
Ectoparasites on cave-dwelling bats of the family Vespertilionidae.
behavior
Adults stay on host except to deposit pupae in roost.
feeding ecology and diet
Hematophagous.
reproductive biology
Females deposit fully developed pupae singly, gluing them to vertical substrata (e.g., cave walls and trees) in the vicinity of the host bat roosts. This process may be repeated several times during the female's lifetime. Emergence of the adult is triggered by the warmth or contact of a roosting bat.
conservation status
Not threatened.
significance to humans
None known.
Horse bot fly
Gasterophilus intestinalis
family
Oestridae
taxonomy
Oestrus intestinalis De Geer, 1776, type locality not specified (probably Sweden).
other common names
English: Nit fly; German: Magenfliege, Magendasselfliege.
physical characteristics
Adults resemble honeybees in appearance and size (about 0.7 in [18 mm]). They have a hairy head and predominantly yellow-brown hairs dorsally, and whitish ones laterally on the thorax. The abdomen is tricolored, bearing long white hairs on the second segment, predominantly black ones on the third and fourth segments, and dark yellow hairs on the posterior parts. The light yellow eggs are attached to the hair of the host. Larvae are reddish brown and when mature usually around 0.8 in (20 mm) in length. They have two bands of coarse spines with blunt tips per segment (except in the last segment).
distribution
Originally from the Old World, horse bot flies today are virtually cosmopolitan, having spread with humans and their horses around the world.
habitat
Associated with their hosts.
behavior
Adults are diurnal (active in the daytime) with peak activity occurring in the early afternoon in warm, sunny weather.
feeding ecology and diet
Adult mouthparts are greatly reduced; adults do not feed and rely on stored body fats. Larvae infest the digestive tract of horses and other domestic animals such as mules and donkeys, where they feed on tissue in the horse's stomach or gut lining as well as on nutrients from the horse's food. Newly hatched larvae occasionally invade human skin but die in a few days.
reproductive biology
Adults are short-lived; females have a life span of one day. Mating occurs in the vicinity of horses where solitary hovering males will establish and defend a territory. They are also known to aggregate at hilltops and other elevated landmarks to mate, where males hover and aggressively pursue passing objects. Males make contact with a female on the wing, couple, and fall to the ground, where copulation is completed. Females lay eggs around the knees of walking, trotting, or standing horses; if this action induces the horses to gallop, the females will pursue them until they stop and then immediately resume oviposition. When the horse licks the area, the heat and wetness from its tongue causes the eggs to hatch. The larvae then enter the mouth and travel to the stomach, where they attach themselves with strong mouth hooks to the walls. Third-stage larvae remain attached for 9 to 11 months before exiting within the horse's feces. Pupation takes place on the ground, lasting for 3–5 weeks.
conservation status
Not threatened.
significance to humans
Because of their parasitic habit in horses, larvae are more easily found than adults. They cause hide spoilage, ulceration, hemorrhage, severe debilitation, and even death in horses in cases of severe infestations.
Fire ant decapitating fly
Pseudacteon curvatus
family
Phoridae
taxonomy
Pseudacteon curvatus Borgmeier, 1925, Brazil.
other common names
None known.
physical characteristics
Small, about the size of their host ant's head, with relatively large eyes, a humped-back thorax, and a hypodermic needle-shaped ovipositor in females. In the field, they appear as minute, fuzzy specks hovering over host ants.
distribution
South America from Brazil to Argentina.
habitat
Widely distributed in the natural range of their hosts.
behavior
Females are attracted to disturbed mounds, mating flights, or foraging trails of their hosts. Females in attack mode hover 0.1–0.4 in (3–10 mm) above the ants and orient to their movements. Males are not attracted to the ants.
feeding ecology and diet
Adults feed on nectar, and the larva on the inner tissues of its host ant's head.
reproductive biology
Males and females have multiple matings. The females lay eggs in fire ants of the Solenopsis saevissima species-complex. The female stays in front of a chosen worker ant and then quickly moves to the side of the ant and injects a single egg into its thorax. The larva migrates to the head capsule of the worker and passes through three instars, during which time the worker ant appears to behave normally. Just before pupation, the tissue inside the ant's head capsule is consumed, killing the ant in the process. Larval and pupal development each takes 2–3 weeks. The ant's head usually falls off, and the pupa completes its development inside the head capsule, at which point the adult fly emerges from its oral cavity. Sex in this species is apparently determined environmentally, as males are produced from smaller ant workers, whereas females are produced from larger ant workers. Adults are active all year, except during the winter months in the more temperate regions of their range.
conservation status
Not threatened.
significance to humans
Possible biological control agent for red imported fire ants in the United States. Although the percentage of ants that the flies are able to parasitize and kill is low, they have a large effect on their host's competitive interactions with other ants. The presence of ant decapitating flies disrupts colony-level foraging in the ants, which retreat to their nests, leading to as much as a 50% decrease in resource acquisition.
Dawson River black fly
Austrosimulium pestilens
family
Simuliidae
taxonomy
Austrosimulium pestilens Mackerras and Mackerras, 1948, Queensland, Australia.
other common names
None known.
physical characteristics
Adults are small, black, and humped-back, about 0.04 in (1 mm) in length. Eyes are holoptic (in contact with each other) in males and dichoptic (separated) in females. The larvae are 0.008–0.2 in (0.2–4.5 mm) in length, pale with irregular mottling. They have a pair of large cephalic fans on the head, a proleg (false leg) in the thorax, and another one at the tip of the abdomen, armed with a circlet of spines that anchors the larvae to submerged substrates. Pupae have a pair of breathing organs called spiracular gills that look like a collection of threads attached to the back of the head, which enable them to breathe while permanently submerged.
distribution
Queensland and northern New South Wales in Australia.
habitat
Larvae require oxygenated, running waters, and they live in both stony and weedy streams. Adults appear along the larval river or streams courses and the surrounding countryside.
behavior
After mating, females look for a blood meal in open spaces, seldom entering buildings. Following the blood meal, females rest in trees and shrubs prior to oviposition.
feeding ecology and diet
Larvae filter drifting food with their fan-like mouthparts. Adult females require a blood meal before the first batch of eggs is laid. They are pool feeders, imbibing blood from a droplet created from cutting the skin.
reproductive biology
Eggs are laid into fresh running water and sink to the bottom, where they can remain quiescent for at least five years on a damp stream bed, until they hatch with the next flood. Larvae construct well-formed silken cocoons when ready to pupate; the pupal stage lasts about two days. Adults usually emerge during daylight hours and float to the surface in a bubble of air. Males tend to emerge before females and form highly visible mating swarms associated with trees close to the water. Females enter these swarms, are captured, and mate, after which they seek a blood meal. Egglaying swarms are diffuse and occur throughout the daylight hours. Females fly low over the stream and dip their abdomens into the water surface. Adult flies may live up to three weeks.
conservation status
Not threatened.
significance to humans
Considered a nuisance pest in Australia; females bite cattle, dingoes, goats, horses, humans, and marsupials such as kangaroos and wallabies.
Chevroned hover fly
Allograpta obliqua
family
Syrphidae
taxonomy
Scaeva obliqua Say, 1823, United Sates.
other common names
None known.
physical characteristics
Eggs are white, elongate, and oval. The mature larvae are 0.35 in (8–9 mm) in length, elongate and flattened on the dorsum, green with two narrow whitish longitudinal stripes and with transversely wrinkled tegument-bearing papillae. They have mouth hooks on the anterior end of the tapering head, and two posterior respiratory tubes fused together. The pupae are green, darkening at maturity. Adults are 0.25 in (6–7 mm) in length. They have a yellow face, yellow thoracic stripes, and four longitudinal, oblique, yellow stripes or spots on the fourth and fifth abdominal segments. Eyes are holoptic (in contact with one another) in males and dichoptic (separated) in females.
distribution
Canada south to Argentina.
habitat
Found in areas with flowering plants sheltered from wind.
behavior
Adults are excellent fliers and can hover and fly backward.
feeding ecology and diet
Adults often visit flowers for nectar or may be seen around aphid colonies feeding on honeydew secreted by the aphids. Larvae prey on aphids, but if there are no aphids, they can subsist on plant materials such as pollen.
reproductive biology
Adults occur throughout the year in temperate areas, and during spring and summer in the cooler areas of their range. The eggs are laid singly on the surface of a leaf or twig that bears aphids. They hatch in 2–8 days. The larval stage takes 5–20 days, and larvae fasten themselves to a leaf or twig when ready to pupate. The pupal stage takes 8–33 days.
conservation status
Not threatened.
significance to humans
This flower fly is considered to be beneficial to humans, because adults are agents in the cross pollination of some plants, and the larvae are predators of aphids that attack citrus, subtropical fruit trees, grains, corn, alfalfa, cotton, grapes, lettuce and other vegetables, and ornamentals. When larval populations are high, they may consume 70–100% of the aphid populations.
Big black horse fly
Tabanus punctifer
family
Tabanidae
taxonomy
Tabanus punctifer Osten Sacken, 1876, Utah.
other common names
English: Klegs, green heads.
physical characteristics
Adults are stout and broad-headed, 0.35–1.1 in (9–28 mm) in length, with bulging and brightly colored eyes, gray thorax, black abdomen, and blackish wings. Larvae are cylindrical and have a longitudinally striated tegument.
distribution
Canada from British Columbia south to California, encompassing the western United States from Kansas south to Texas.
habitat
Adults are especially common around ponds, streams, and marshes, where the larvae live in shallow water or moist soil.
behavior
Adults land stealthily on exposed skin in order to feed.
feeding ecology and diet
Adults feed mainly on nectar and flower pollen, and females need a blood meal before they can lay eggs. They have mouth-parts adapted for tearing and lapping, and they suck blood mainly from livestock but also from humans. Larvae are predacious, feeding on insect larvae, snails, and earthworms.
reproductive biology
Eggs are laid in 3–4 layer masses of 100–1,000 eggs each, covered with a jellylike material, on leaves, rocks, or debris overhanging water or on moist areas. Upon hatching, the larvae fall into the water or onto moist soil, where they undergo 3–4 instars. When ready to pupate, they move to the margin of the pool or drier areas of their habitat.
conservation status
Not threatened.
significance to humans
Considered a nuisance pest for horses and mules because of the painful bites of females, which occasionally also bite humans.
Mediterranean fruit fly
Ceratitis capitata
family
Tephritidae
taxonomy
Trypeta capitata Wiedemann, 1824, East Indies (probably in error).
other common names
None known.
physical characteristics
Adults range from 0.14–0.2 in (3.5–5 mm) in length. The wings are semiopaque, broad, and patterned with yellow, and the eyes
are iridescent and multicolored. Males are distinguished by a pair of spatulate projections on the frons, and females by a prominent ovipositor. Larvae are white and cylindrical, with a narrowed anterior end and flattened caudal end, and reach 0.3–0.35 in (7–9 mm) in length. Pupae are cylindrical, approximately 0.12 in (3 mm) in length, and dark reddish brown.
distribution
Native to Africa. Within the last 100 years, has spread throughout most of the world, from Portugal, Spain, Italy, Greece, Jordan, Turkey, parts of Saudi Arabia and most countries along the North African coast as far away as the Americas, the Hawaiian islands, and Australia, mainly due to transportation of infested fruit. It was eradicated from Mexico using the Sterile Insect Technique, which has also been employed effectively in Guatemala, Chile, California, and Florida.
habitat
Found wherever appropriate host trees (including citrus, peach, and guava, among many others) grow.
behavior
Adults can fly only short distances, but winds may carry them a mile or more away.
feeding ecology and diet
Larvae feed within the flesh of fruits where eggs are laid, and adults on exposed sweet substances such as fruit, honeydew, or plant sap.
reproductive biology
Eggs are laid beneath the skin of a suitable fruit in batches of 1–10. Females will lay approximately 300 or more eggs during their lifetime; these hatch into first-instar larvae after 2–3 days. The larvae live and feed within the host fruit, undergoing two molts in 6–10 days. When ready to pupate, the third-instar larvae emerge from the fruit and drop to the ground, where they pupate in soil 1–2 in (2.5–5 cm) below the surface. The adults emerge from the pupa approximately 10 days later. They exhibit a "lek" mating system, in which males settle nonrandomly on particular host or nonhost trees and defend individual leaves as mating territories. While on territory, males emit a pheromone attractive to females and, following female arrival, perform a brief courtship display involving wing and head movements before mounting the female.
conservation status
Not threatened.
significance to humans
The mediterranean fruit fly is a major agricultural pest in temperate and subtropical regions worldwide, attacking over 200 varieties of cultivated fruit crops.
European marsh crane fly
Tipula paludosa
family
Tipulidae
taxonomy
Tipula paludosa Meigen, 1830, Europe.
other common names
English: Leatherjacket (larvae), marsh crane fly; German: Lästlinge Wiesenschnake; Italian: Tipula dei prati.
physical characteristics
Adults resemble giant mosquitoes and have a grayish brown body, about 1 in (2.5 cm) in length, two narrow wings, and very long (0.7–0.9 in [17–25 mm]) brown legs. Larvae are gray, 1.1 in (30 mm) in length, and are known as leatherjackets because of their tough leatherlike skin. Pupae are brown, spiny, and about 1.3 in (33 mm) in length.
distribution
Native to northern Europe; introduced into western Canada and United States.
habitat
Found in wet areas of lawns, pastures, fields of forage crops, and grassy banks of drainage ditches, in regions of mild winters, cool summers, and rainfall averaging about 23.5 in (600 mm).
behavior
Adults are weak fliers. They are attracted to lights and may enter houses and buildings.
feeding ecology and diet
Young larvae feed on humus and rotting vegetable matter, germinating cereal seeds, roots of Gramineae (grass), and the collar area of some young aerial plants.
reproductive biology
The marsh crane fly completes one generation per year. Adults are abundant in late August and early September, and each female can lay up to 280 black, shiny eggs, mainly at night, from mid-July to late September. Eggs are laid on the soil surface or at depths of less than 0.4 in (1 cm), and hatch 11–15 days following oviposition. Larvae are found in the upper 1.1 in (30 mm) of soil, throughout the fall and during warm periods in winter. They grow rapidly in spring and reach their full length of about 1.6 in (40 mm) by April or May, pupating approximately in mid-July. Pupae remain underground for about two weeks before working their way to the surface, where the empty pupal case is often left protruding from the soil by the emerging adult. Adults emerge after sunset and mate immediately. Males live about 7 days; females 4–5.
conservation status
Not threatened.
significance to humans
Of economic importance due to larvae, which can strip the root hairs and girdle the stems of bareroot stock in commercial tree nurseries.
Resources
Books
Colless, D. H., and J. F. McAlpine. "Diptera." In The Insects of Australia: A Textbook for Students and Research Workers, vol. 2 (CSIRO), 2nd ed. Carlton, Australia: Melbourne University Press, 1991.
Evenhuis, N. L. Catalogue of the Fossil Flies of the World (Insecta: Diptera). Leiden, Netherlands: Backhuys Publishers, 1994.
——. Litteratura Taxonomica Dipterorum (1758–1930). 2 vols. Leiden, Netherlands: Backhuys Publishers, 1997.
Foote, B. A., F. C. Thompson, G. A. Dahlem, D. S. Dennis, T. A. Stasny, and H. J. Teskey. "Order Diptera." In Immature Insects, vol. 2, edited by F. W. Stehr. Dubuque, IA: Kendall/Hunt Publishing, 1991.
Haupt, J., and H. Haupt. Fliegen und Mücken: Beobachtung, Lebensweise. Augsburg, Germany: Naturbuch-Verlag, 1998.
McAlpine, J. F., et al., eds. Manual of Nearctic Diptera. 3 vols. Ottawa, Canada: Research Branch, Agriculture Canada, 1981–1989.
Oldroyd, H. The Natural History of Flies. New York: W.W. Norton and Company, 1965.
Organizations
Arbeitskreis Diptera. Dr. Frank Menzel (Leiter), ZALF e.V., Deutsches Entomologisches Institut, Postfach 100238, Eberswalde, D-16202 Germany. Phone: 03334-589820. Fax: 03334-212379. E-mail: [email protected] Web site: <http://www.ak-diptera.de>
Dipterists' Forum. Liz Howe, Ger-y-Parc, Marianglas, Benllech, Gwynedd, LL74 8 NS United Kingdom. Web site: <http://www.dipteristsforum.org.uk/>
North American Dipterists' Society. E-mail: [email protected]
The Malloch Society. Graham Rotheray, Research Coordinator, Royal Museums of Scotland, Chamber Street, Edinburgh, EH1 1JF United Kingdom. E-mail: [email protected]
Other
"BIOSIS." Resource guide: Diptera [May 28, 2003]. <http://www.biosis.org/zrdocs/zoolinfo/grp_dipt.htm>.
"The Diptera Site." Systematic Entomology Laboratory, ARS, USDA: Department of Systematic Biology, National Museum of Natural History [May 28, 2003]. <http://www.sel.barc.usda.gov/diptera/diptera.htm>.
"Diptera. Tree of Life Web Project." 2001 [May 28, 2003]. <http://tolweb.org/tree?group=Diptera&contgroup=Endopterygota>.
Web version of the "Catalog of the Diptera of the Australasian and Oceanian Regions." September 23, 1999 [May 28, 2003]. <http://hbs.bishopmuseum.org/aocat/aocathome.html>.
Natalia von Ellenrieder, PhD