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Home , Anthomyzidae, Asteiidae, Australimyzidae, Axymyiidae, Bibionomorpha, Biology of Diptera

, GNATS, AND MOSQUITOES

Brian V. Brown Natural History Museum of Los Angeles County

I. Introduction moths; 120,000 ), and Hymenoptera (ants, bees, II. Major Subdivisions wasps, and sawflies; 130,000 species)—they form the III. Life History Diversity largest aggregation of species on the planet. Each of IV. Conservation these megadiversity groups has more species assigned to it than to any other group of organisms except plants (300,000 species). Like other , most species of Diptera are still undescribed, and the actual number GLOSSARY could range as high as 1 million or more species. Diptera are found on every continent, including Ant- Diptera Group of insects to which the flies, including arctica. The relative percentage of Diptera within the gnats and mosquitoes, belong. fauna rises with latitude (and elevation) as other, (pl. larvae) Immature stage of flies, often less cold-adapted taxa are lost; for instance, over one- called maggots. half of all insect species recorded from the Canadian high arctic are Diptera. The extant species of all biogeo- graphical regions have been cataloged (Table I), as have the fossil Diptera. Some catalogs are badly outdated and THE DIPTERA, or true flies, are a well-established, the number of species described for each region is often monophyletic group of insects with more than 124,000 more indicative of the amount of taxonomic activity extant species. They are found worldwide and interact directed at a given fauna than the true diversity. For with the environment at almost all trophic levels as instance, the Palearctic Region is the best studied and scavengers, filter-feeders, , predators, parasi- has more described species than the relatively poorly toids, and parasites. known, but presumably more diverse, Neotropical Region. Therefore, conclusions about dipteran bioge- ography based on these numbers will be highly inac- I. INTRODUCTION curate. Diptera are a well-established monophyletic group, The insect Order Diptera, with more than 124,000 cur- with the most obvious defining character being the rently described, extant species, ranks as one of the reduction of the hind wings to small, club-shaped organs worlds largest groups of organisms. Along with the called halteres. The insect orders considered to be most other insect megadiversity groups—Coleoptera (bee- closely related to Diptera are Siphonaptera (fleas) and tles; 350,000 species), (butterflies and Mecoptera (scorpionflies), although recent molecular

Encyclopedia of Biodiversity, Volume 2 Copyright  2001 by Academic Press. All rights of reproduction in any form reserved. 815 816 FLIES, GNATS, AND MOSQUITOES

TABLE I lished, are given in Table II. Many families lack common Biogeographical Regions and the Number of names, including the second largest family in the order Described Diptera Species (). That a group with more described species than the mammals lacks a common name is a good Number Region of species indication of the lack of general appreciation for the importance and ubiquity of the Diptera. The number Nearctic 25,000 of described species in each family is given, but in Neotropical 20,000 many instances these numbers are badly out of date Palearctic 29,000 and should be considered a bare minimum. Certainly, Afrotropical 16,318 in most families of Diptera there are a large number of Australasian 15,764 undescribed species awaiting the attention of special- Oriental 15,964 ists. It is estimated that we have described only 10% or Antarctica 60 fewer of the species in many families. The Diptera are traditionally organized into three Compiled from the various catalogs. suborders: the , the orthorrhaphous , and the cyclorrhaphous Brachycera. Of these, it is likely that only the is a mono- research indicates that the highly aberrant Strepsiptera phyletic, or natural, group. Although a consensus on (twisted-wing parasites) may be their closest relatives. the higher relationships within the Diptera is not yet Fossil Diptera are common in the amber faunas of available, it is generally agreed that the ‘‘Nematocera’’ the world, which however extend back in time only is a paraphyletic assemblage of relatively primitive dip- to the early . The oldest dipteran fossil is teran families and that some subgroup of this assem- believed to be from at least the mid-. blage is more closely related to the Brachycera than to Like the other megadiversity groups, the Diptera other nematocerans. Similarly, within the Brachycera, are holometabolous insects, with a separate egg, larva, a group widely considered to be monophyletic, the or- , and adult stage. Generally, most feeding takes thorrhaphous families are now believed to be a paraphy- place in the larval stage, whereas the adult is usually letic assemblage relative to the Cyclorrhapha. Finally, specialized for reproduction and dispersal. Some adult within the Cyclorrhapha is a group of flies traditionally Diptera are voracious feeders, however, requiring sub- called the (here called the lower Cyclorrhapha), stantial supplemental feeding to mature their eggs or which is probably paraphyletic with respect to the power their flight. monophyletic . The details of the phylog- Flies are common in natural, disturbed, and urban eny of the Diptera has been reviewed extensively by habitats. Larvae are found on land and in freshwater; Yeates and Wiegmann and their discussion of various there are relatively few marine or brackish water spe- groups is highly recommended for understanding the cies. Some species are synanthropic and have been current status of dipteran phylogeny. transported around the world with human activities. Within the Diptera, higher taxa show repeated pat- Diptera are the most important vectors of human and terns of relatively primitive, nondiverse grades of orga- disease, and a few plant-feeding species have nization with relatively highly derived, speciose sister become agricultural pests. The life history of most spe- taxa. Thus the lower Diptera are collectively much less cies of flies, however, is unknown. The group is so diverse than the Brachycera, with the notable exception large, and there are so many undescribed species, that of the incredibly large family Tipulidae. Within the the science of dipterology is still in its relative infancy. Brachycera, the is by far the largest in- fraorder and the Schizophora has four times more spe- cies than the lower Cyclorrhapha. The numbers are II. MAJOR SUBDIVISIONS less disparate in the Schizophora, with about 26,000 acalypterates and 19,000 calypterates, but the mono- Table II presents a general list of the families of Diptera phyly of the acalypterates is highly contentious, making and some of the higher taxa that contain them. This list such a comparison questionable. is based on only one of several possible classifications, The distribution of species among the families of however, and cannot be considered the final word in Diptera is extremely divergent, with the largest number dipteran groupings. Common names, where well estab- found in the Tipulidae and the Tachinidae. Together, FLIES, GNATS, AND MOSQUITOES 817

TABLE II Simplified List of Major Subgroups and Families of Diptera

Number Common name of species

(Nematocerous groups؍) Lower Diptera Infraorder Phantom crane files 61 42 Infraorder Superfamily Culicidae Mosquitoes 3,000 Meniscus midges 175 61 Phantom midges 50 Superfamily Biting midges 5,360 Midges 5,000 Simuliidae Black files 1,475 121 Infraorder Blephariceromorpha Net-winged midges 300 Deuterophlebiidae Mountain midges 14 7 Infraorder 5 March flies 675 Gall midges 4,600 gnats 3,000 4 Dark-winged fungus gnats 1,000 Infraorder Tipulidae Crane flies 14,000 Winter crane flies 110 Infraorder Wood gnats 100 Perissomatidae 5 Sand flies, moth flies 2700 255 Synneuridae 4 Brachycera (an unranked taxon) Infraorder Xylophagomorpha 111 Infraorder 90 49 Snipe flies 520 Tabanidae Horseflies, deer flies 3,000 Ant lions 31

continues 818 FLIES, GNATS, AND MOSQUITOES

continued

Number Common name of species

Infraorder Stratiomyomorpha 20 Soldier flies 2,500 107 Infraorder Muscomorpha Superfamily Small-headed flies 500 Tangle-veined flies 250 Superfamily Apioceridae Flower-loving flies 145 Robber flies 5,600 Bee flies 4,800 Mydidae Mydas flies 353 Window flies 330 Stiletto flies 850 Superfamily Dolichopodide Long-legged flies 5,100 Dance flies 3,500 Cyclorrhapha (an unranked taxon of Muscomorpha) ‘‘Lower Cyclorrhapha’’ (ϭAschiza of previous authors) 1 Spear-winged flies 35 3 Humpbacked flies, scuttle flies 3,200 Big-headed flies 600 Flat-footed flies 215 Sciadoceridae 2 Syrphidae Hover flies, flower flies 5,800 Schizophora ‘‘Acalypterates’’ (possibly not monophyletic) Superfamily 30 Stilt-legged flies 500 Cactus flies 110 Superfamily Diopsidae Stalk-eyed flies 153 13 Nothybidae 8 Rust flies 200 Somatiidae 7 27 Syringogastridae 8 18 Superfamily Conopoidea Thick-headed flies 800 Superfamily 700 Otitidae 800 continues FLIES, GNATS, AND MOSQUITOES 819 continued

Number Common name of species

Pallopteridae 52 Skipper flies 71 1,000 200 170 Tachiniscidae 3 Fruit flies 4,000 Superfamily flies 90 Aphid flies, silver flies 250 Eurychoromyiidae 1 1,550 Superfamily Seaweed flies 30 30 23 Marsh flies 515 30 Black scavenger flies 240 Superfamily Suprafamily Clusioinea 3 217 Suprafamily Agromyzoinea Leafminer flies 3,500 Fergusoninidae 25 50 Suprafamily Opomyzoinea 49 Marginidae 2 40 Suprafamily Asteioinea 100 25 Upside-down flies 5 19 5 8 Superfamily 5 Bee lice 7 Beach flies 113 41 Frit flies 2,000 Cryptochaetidae 25 190 Tethinidae 126 continues 820 FLIES, GNATS, AND MOSQUITOES

continued

Number Common name of species

Superfamily 40 (s.l.) 520 Mormotomyiidae 1 Lesser dung flies 2,500 Superfamily 11 36 22 Vinegar flies, pomace flies 2,900 Shore flies 1,300 Superfamily Glossinidae Tsetse flies 22 Louse flies 200 Bat flies 260 Bat flies 220 Superfamily 1,100 265 3,880 250 Superfamily Blow flies 1,000 Mystacinobiidae 1 Oestridae Bot flies, warble flies 42 100 Sarcophagidae Flesh flies 2,500 Tachinidae 9,200 TOTAL 124,390

Modified from Yeates and Wiegmann (1999) and McAlpine (1989). Most important taxa are in bold. Approximate number of described species from various sources.

these families account for almost 20% of the species in thropods, mostly other insects and, within the insects, the order. mostly larval Lepidoptera. Eggs are either laid on or in The Tipulidae, or crane flies, are elongate, long- the host or are broadcast in suitable areas. Larvae hatch legged, somewhat fragile flies that are found nearly from broadcast eggs and wait in ambush for hosts. Some everywhere on earth. The adults are sometimes found tachinids produce microtype eggs that are designed to at lights but are most often seen resting on vegetation. be ingested by the hosts; these eggs hatch inside the The larvae have a variety of habitats, including terres- host and penetrate the gut wall to enter the body cavity. trial—in soil, , and decaying wood—freshwater, Adult tachinids are stout, bristly, housefly-like flies that and intertidal. They are scavengers, herbivores, or pred- are seen frequently on vegetation or flowers. ators. There are another 21 families of Diptera that can In contrast to the eclectic habits of the Tipulidae, be considered large, possessing about 2000 or more larvae of Tachinidae have a single way of life: parasitism. described species. Together, these 23 largest families All known species are internal of other ar- (including tipulids and tachinids) comprise about FLIES, GNATS, AND MOSQUITOES 821

100,000 species, or approximately 80% of the Order predatory. Some species are saprophagous in early larval Diptera. In order of decreasing number of species, these instars, becoming carnivorous later. other 21 large families are as follows: • Agromyzidae: leaf-miner flies (3500 spp.). Along with some other insects, larvae of many species of agro- • Syrphidae: hover flies, flower flies (5800 spp.). myzids feed within plant leaves, excavating the distinc- Adults of this family often are brightly colored mimics tive, light-colored tunnels called mines. The adults are of Hymenoptera (bees and wasps). The larvae are sa- small, usually dark-colored flies; some species are prophagous, predatory, or herbivorous. Some saproph- marked with yellow. agous species are called rat-tailed maggots because of • Empididae: dance flies (3500 spp.). Adults of this their elongate posterior breathing tubes. Many of the family are found mostly in damp terrestrial habitats, predatory species live exposed on plants, feeding on often near water. Common and diverse in temperate aphids. regions, they are less prevalent in tropical lowland for- • Asilidae: robber flies (5600 spp.). The adults are ests. Larvae and adults of both sexes are predatory; voracious predators that usually attack their prey while larvae of a few species are parasitoids of caddisfly larvae. in flight, stabbing them with their heavily sclerotized, • Phoridae: humpbacked flies, scuttle flies (3200 swordlike proboscis and injecting digestive fluids. The spp.). Phorids are common and diverse nearly every- larvae are also predatory. where except Antarctica. Larvae can be predators, para- • Ceratopogonidae: biting midges (5360 spp.). The sitoids, true parasites, herbivores, or scavengers. Many tiny adult females of this family require blood meals to species are associated with social insects. mature their eggs. Some species bite vertebrates, other • Tabanidae: horseflies, deer flies (3000 spp.). Adult feed on large insects, and still others are predatory on female tabanids are well-known blood feeders, although small insects. The larvae are predacious, living in damp some species feed only on nectar. The larvae are preda- terrestrial or freshwater habitats. tory, usually found near water. • : long-legged flies (5100 spp.). • Culicidae: mosquitoes (3000 spp.). Adult females These flies are often metallic green in color and are bite vertebrates to obtain blood meals, and they often found commonly on undergrowth or on tree trunks. transmit diseases. Larvae are aquatic. The larvae and adults are predatory. • Mycetophilidae: fungus gnats (3000 spp.). Adults • Chironomidae: midges (5000 spp.). These flies are are found mostly in humid, forested areas. The larvae among the most abundant benthic invertebrates in feed mainly on fungi, although some species spin webs freshwater environments; some are also terrestrial or to capture insect prey and a few species are parasitoids intertidal. The adult males often form enormous mat- of flatworms. ing swarms. • Drosophilidae: vinegar flies, pomace flies (2900 • Bombyliidae (including ): bee flies spp.). This family is best known for Drosophila melano- (4800 spp.). Species of this family are most diverse in gaster, the ubiquitous model organism for genetic re- dry areas, including deserts, and are nearly absent from search. Although adults are commonly found around tropical rain forests. The larvae are parasitoids of the overripe fruit or on mushrooms, the larvae of this family immature stages of various other insects or predatory have a variety of lifestyles, from saprophagy to parasit- on grasshopper egg pods. ism and predation. • Cecidomyiidae: gall midges (4600 spp.). Cecido- • Psychodidae: moth flies (2700 spp.). The scaveng- myiids are generally considered one of the largest, yet ing larvae of these flies are usually found in moist condi- most poorly known groups of Diptera. Larvae often tions, in soil, rotting wood, or other decaying vegeta- form galls on various plants, but there are non-gallform- tion. Adults of one subfamily are blood feeders and ing species and many mycophagous forms as well. transmit the disease leishmaniasis to humans. • Tephritidae: fruit flies (4000 spp.). Larval tephrit- • Sarcophagidae: flesh flies (2500 spp.). Sarcophagid ids are phytophagous, attacking a wide variety of plants larvae are saprophagous, parasitoids, predators or com- and sometimes forming galls. The adults often have mensals in the nests of solitary Hymenoptera. The color patterns on their wings. adults of some species are associated with filth. • Muscidae: houseflies and relatives (3880 spp.). A • Sphaeroceridae: lesser dung flies (2500 spp.). Lar- few extremely well-known muscid species are synan- vae and adults of this family are commonly found on thropic, especially Musca domestica and Stomoxys dung, carrion, and decaying organic material. calcitrans. Larvae of most species live in decaying or- • Stratiomyidae: soldier flies (2500 spp.). The adults ganic material, where they are either saprophagous or of this family are often brightly colored and conspicuous 822 FLIES, GNATS, AND MOSQUITOES on flowers. The larvae are often found near water, in encountered in soil (including sand), dead wood, dung, decaying organic material, or under bark. They are sa- carrion, decaying vegetation, and among the refuse of prophagous, herbivorous, or predatory. social insect colonies. Relatively few are found living • Chloropidae: frit flies (2000 spp.). Larvae of chlo- exposed on vegetation, including some herbivorous ti- ropids have nearly every conceivable way of life, from pulids and many aphidophagous syrphids. Aquatic scavenging to predation, parasitism and herbivory, al- forms are found on the bottom and in the water column though there are many more plant feeders in this family of lakes, streams, and ponds. Larval Diptera are preda- than the similarly diverse Phoridae. tors, scavengers, herbivores, parasitoids, or even true parasites. A. Nematocerous Families 1. Scavengers The nematocerous families are the relatively primitive This is the lifestyle most commonly associated with members of the Diptera, characterized by long, uncon- Diptera larvae, especially those of the Brachycera. More solidated antennae consisting of many segments. There than half of the 128 families recognized herein have are 26 families in this group and approximately 40,000 larvae that feed on decaying organic material or organic species included. Many are associated with aquatic habi- detritus. Most receive their nutrition from bacteria and tats and some, such as mosquitoes, black flies, and other microorganisms of decay, not from the main sub- biting midges, are voracious blood feeders. stance on which they are found. They concentrate these organisms and other suspended particles with a B. Brachycera sievelike pharyngeal filter. Most Diptera belong to the Brachycera, a group charac- Among the most obvious terrestrial scavengers are terized by the reduction or fusion of antennal segments the larvae of blow flies (Calliphoridae) that are found to eight or fewer and by modifications to the larval head on newly dead animal carcasses. Early stages of decay and mouthparts. With about 80,000 described species, are characterized by large numbers of calliphorid and this group contains many of the best known flies, such muscid larvae, followed later by drosophilids, fanniids, as houseflies and fruit flies. phorids, piophilids, sepsids, sphaerocerids, and others The lower Brachycera includes several lineages con- as decay proceeds. The fauna of buried carrion is differ- stituting approximately 30,000 species. The larvae of ent, with the calliphorids largely excluded. Instead, the most species are predatory, although there are a few muscid Muscina, various phorids, and sphaero- groups as well. The most familiar are the cerids predominate. The fauna of carrion immersed in large families Asilidae, Bombyliidae, Tabanidae, Doli- water has also been studied and found to differ from chopodidae, and Empididae. that on dry land. There has been considerable study of The Cyclorrhapha, with about 50,000 species, in- the succession of scavenging Diptera larvae on dead cludes a few primitive lineages and the Schizophora. , leading to the potential for their use in foren- The primitive groups are relatively small, with the ex- sic entomology. ceptions of the large families Phoridae and Syrphidae. Decaying vegetable matter is also rich in scavenging Within the Schizophora, there are a plethora of smaller Diptera, especially muscids, sphaerocerids, sciarids, and acalypterate families that are rare, but many, such as others. Some muscids are obligate thermophiles, requir- the Tephritidae, Agromyzidae, Drosophilidae, Sphaero- ing the heat generated by the decay of large piles of ceridae, and Ephydridae, are abundant and commonly compost. Decaying seashore vegetation supports coe- encountered. The Calyptratae includes the familiar lopids, sphaerocerids, and anthomyiids. Rotting fruit is houseflies, flesh flies, and blow flies as well as the speci- the food of drosophilids, stratiomyids, and some ose parasitoids of the Tachinidae. Also included are phorids. a number of mammal parasites, including some truly In aquatic environments, many larval Diptera feed on bizarre, -like bat parasites in the Nycteribiidae small organic particles in the water or on the substrate. and Streblidae. Larvae of Culicidae and Simuliidae filter particles from the water with their brushlike labral fans. III. LIFE HISTORY DIVERSITY 2. Herbivores Diptera that feed on living plants (including algae and A. Larvae fungi) are found in 37 of the 128 families recognized The larvae of flies are abundant and widespread in herein. Some, such as Agromyzidae, Anthomyiidae, Bib- most terrestrial and aquatic habitats. They are often ionidae, Cecidomyiidae, Chloropidae, Phoridae, Psili- FLIES, GNATS, AND MOSQUITOES 823 dae, Sciaridae, Tephritidae, and Tipulidae, include spe- on the nectar in flowers, or on honeydew, the sweet cies considered to be pests to human agriculture. secretions of Homoptera. Some flies require nitrogen for larvae attack all parts of plants, including fruits, flowers, nourishing their eggs and are thus avid flower visitors in stems, leaves (as leaf-miners), and roots. search of pollen. Flower foraging for nectar and pollen makes Diptera adults important of plants. 3. Predators At least some parasitoids feed on the hemolymph of Predators are organisms that kill more than a single their hosts after oviposition, and many dipteran species host organism for their feeding. There are 35 families feed on dead insects, carrion, dung, or rotting vegeta- with this way of life, including nearly all of the non- tion. A few adult Diptera, including Deuterophebiidae cyclorrhaphan Brachycera. Most have extremely active and some Oestridae, have vestigial mouthparts and do larvae that attack other invertebrates as their major food not feed. source. The larvae of tabanids have been known to kill Adults of a number of families have species that are frogs, an interesting reversal of the usual chain of well-known blood feeders, especially most or all species events. Many predatory dipteran larvae are beneficial of Ceratopogonidae, Culicidae, Glossinidae, Hippobos- to humans in controlling insects considered to be pests. cidae, Nycteribiidae, Simuliidae, Streblidae, and Taba- Examples include syrphids attacking aphids and preda- nidae. Other families with fewer blood-feeding species tory muscid larvae that kill larvae of other muscids, are Muscidae, Rhagionidae, and Athericidae. such as houseflies. Some families of Diptera have species that are preda- tory as adults. This lifestyle is especially well developed 4. Parasitoids in the Asilidae, Dolichopodidae, and Empididae but Parasitoids develop on and kill a single host. Twenty- also occurs in some other families, such as Muscidae two families of Diptera have this way of life, which was and Phoridae. reviewed recently by Feener and Brown. All species of the second largest family of Diptera, the Tachinidae, are parasitoids. All dipteran parasitoids attack other C. Special Associations invertebrates, usually other insects, but unusual hosts 1. Aquatic Diptera include terrestrial flatworms, mollusks, , millipedes, , and scorpions. The larvae of many nematocerous families, as well as some Brachycera, are found in freshwater habitats. 5. Parasites Among the most consistently aquatic forms are those Parasites feed on a single host, but do not normally kill families in the Culicomorpha and Blephariceromorpha, it. True parasites include the bot flies, whose larvae including such well-known families as Culicidae (mos- live under the skin or in the nasal cavities of various quitoes), Simuliidae (black flies), and Chironomidae mammals, including humans. Some bot fly larvae live in (midges). Chironomidae in particular can be exceed- the stomachs and alimentary tracts of horses, elephants, ingly abundant, and various species assemblages are zebras, and rhinos. Other parasites of vertebrates are often used for assessment of water quality. The larvae calliphorids, chloropids, piophilids, and muscids. True of Simuliidae and Blephariceromorpha are found almost parasites of invertebrates are less well known but occur exclusively in clean, running water, with the Deuter- in a few families, such as Phoridae. ophlebiidae and Blephariceridae being especially adapted to fast-flowing streams. Larval Culicidae are 6. No Free-Living Larvae often found in ephemeral ponds that appear after snow- The larvae of the four families of the Hippoboscoidea— melt in temperate regions and after heavy rains else- Glossinidae, Hippoboscidae, Nycteribiidae and Strebli- where. dae—are retained in the female abdomen and nourished by secretions of the accessory glands. They are depos- 2. Phytotelmata ited by females as fully mature, third-instar larvae, Phytotelmata are structures of plants that allow accu- which quickly pupariate. mulations of water. They occur in various parts of plants, including leaves, leaf axils (especially of brome- liads and bananas), stems (especially of bamboos), B. Adults fruits, and specialized structures (such as pitchers in Most adult Diptera receive the majority of their nutri- pitcher plants). Among the approximately 20 families tion as larvae and do not feed extensively. Many need of Diptera that utilize phytotelmata, the Culicidae are carbohydrates to power their flight, however, and feed the most prominent, being the most regular and most 824 FLIES, GNATS, AND MOSQUITOES numerous larvae present. The other most frequently fied, with reduced wings, eyes, and body sclerotization. encountered families are Chironomidae, Ceratopogoni- One remarkable genus from Southeast Asia has adult dae, and Psychodidae, but further research has found females that mimic the larvae of their army ant hosts. that other families, such as Phoridae and Tipulidae, Other females are heavily armored and have a rounded, might also be common. Our knowledge of the fauna of teardrop shaped body form. This limuoid body form phytotelmata is still fragmentary and much further allows the females to escape damage when accosted by work needs to be directed at these habitats. aggressive host ants, bees, or termites. The insect trapping structures of pitcher plants Other dipteran larvae found in social insect nests (Nepenthaceae and Sarraceniaceae) frequently harbor belong to the families Braulidae, Calliphoridae, Fannii- dipteran larvae. For instance, a distinctive fauna of dae, Sarcophagidae, Sphaeroceridae, and Syrphidae. about 80 species of aquatic Diptera is specialized to live Most are scavengers, although some are predatory. in the carnivorous pitcher plants of the genus Nepenthes Army ant raids are spectacular tropical phenomena in Southeast Asia. The species found in this habitat are that provide a number of opportunities for dipteran mostly from aquatic groups, such as mosquitoes, but associates. Tachinids and conopids hover or perch near some are from families more usually found in terrestrial the raid front, darting down to parasitize the crickets, habitats—Calliphoridae, Chloropidae, and Phoridae, cockroaches, and other insects flushed by the foraging for example. Nearly all feed on the trapped, drowned ants. Closer to the ground, parasitic phorids dart at insects, or filter microorganisms associated with the their respective hosts: either the army ants themselves decay of such insects from the water. or other ants that are victims of the ant raids. Sarcopha- gids swarm on the leaves of nearby undergrowth, feed- 3. Social Insects ing on the droppings of birds attracted to the insects Social insects are the ants, bees, wasps, and termites flushed out by the ant raids. Often, the raid front is that have organized societies. They have one or a few best identified by listening for the loudest buzzing from females responsible for all the egg laying, while other the activity of hundreds of flies. members of the colony (usually sterile females) gather food and do other tasks. Diptera are associated with 4. Kleptoparasites social insects as scavengers, predators, parasitoids, and Many Diptera exploit other insects or invertebrates that parasites. In the following treatment, only those species sequester or reserve food for long periods of time. By intimately associated with social insects are discussed, waiting before feeding, or by feeding slowly, these hosts whereas opportunistic, generalized predators, such as provide a window of opportunity for larvae or adults robber flies (Asilidae), will be ignored. of flies. The relationship between the host and klepto- Most flies known to be associated with social insects parasite is often developed to such an extent that the are brachycerans. Among the few nematocerous records flies live permanently associated with their food pro- of such associations is the astonishing observation that vider. Phoresy (transportation of the kleptoparasite by some Southeast Asian adults (genus Malaya) the host) often occurs in these associations. feed on honeydew carried in the mouthparts of ant A commonly observed example of workers. and phoresy in Diptera is the association of large spiders Among the Brachycera associated with social insects, and flies. Spider webs provide a continuous supply of the most diverse are the Phoridae. These small flies are food, and often a source of stored insect carcasses for commonly found in association with ants, especially later feeding. This warehouse is exploited by a number army ants (both New World and Old World), termites of fly families, including Ceratopogonidae, Cecidomyii- (especially in Africa and Southeast Asia), and, to a lesser dae, Milichiidae, Chloropidae, Lonchaeidae, Phoridae, extent, social bees and wasps. Many are parasitoids, and Empididae. In many instances, the flies perch on laying their eggs inside the bodies of their adult hosts, the bodies of the spider, waiting for their next meal usually ants, termites, and stingless bees; some are also to arrive. known to parasitize the immature stages of ants. Many Another, much more restricted association occurs are scavengers, living in the refuse piles of the large between dung of the family Scarabaeidae and colonies of army ants and leaf-cutter ants, where they flies of the family Sphaeroceridae. The flies ride on the are joined by scavenging larvae of other families. Some bodies of the dung beetles, waiting until the beetles phorid larvae are predatory on ant brood, as are the find and bury feces for their own larvae to feed upon. larvae of some syrphids. The females of phorid species The flies briefly hop off the beetles, lay their own eggs living in social insect nests are often remarkably modi- on the dung, and then rejoin their food-providing host. FLIES, GNATS, AND MOSQUITOES 825

Kleptoparasites also occur in the nests of social Hy- is still contingent on the recognition and description menoptera, where fly larvae are fed by deceived workers of the many undescribed species. or attack the provisions left for a developing bee, wasp, An exception to these statements is the Syrphidae, or ant larva. A full review of kleptoparasitism is given a group that is popular among amateur collectors, espe- by Sivinski et al. cially in Europe. There, Red Lists of endangered species exist for many regions, including Britain and parts of 5. Swarming the mainland. When species that are at the edge of Swarms of adult Diptera are a common sight in most their distribution are eliminated from consideration, environments. Usually these are aggregations of males, it appears that most endangered syrphids are either allowing females to easily find a mate. Often, swarms saproxylic or associated with wetlands. are seen in the canopy of forests, under overhanging Saproxylic insects of all orders are considered to be branches, in sunlight ‘‘pools’’ in forests, near fire towers among the most endangered insects in Europe. These emerging above tree level, or at the summit of tall hills are species that are obligately associated with rotting or mountains (‘‘hill-topping’’). wood, a habitat that is largely absent from young, even- Most nematocerous families engage in swarming, as aged tree plantations or from older forests that are sani- do about 15 families of Brachycera. Flies that engage tized or managed by removal of dead trees and wood. in this behavior often have associated structural modi- Most of the saproxylic habitats are afforded by old- fications, including a well-developed anal lobe of the growth forests with adequate numbers of injured, bleed- wing and enlarged compound eyes. The development ing, moribund, or dead trees available. Different species of the anal lobe probably allows for better maneuvering of insects are associated with different types of decay, and hovering within the swarm, whereas the increased including whether or not the trees are still standing. size of the eye allows male flies to more precisely place Other variables include whether the trees are large or themselves, and assess their place, within the swarm. small, whether they are exposed to light and low humid- As females choose dominant males within the swarm, ity or are shaded throughout the day, and how long based on their relative position, assessment of position the process of decay has proceeded. Rot holes (some is critical for male mating success. of which contain water), sap runs, dead branches on Species of dance flies (subfamily Empidinae) have otherwise healthy trees, and loosened bark are all micro- elaborated on this basic pattern. Males of many species habitats that have specialized insect (including Diptera) catch prey (usually smaller flies and other soft-bodied faunas. The saproxylic faunas of other regions have not insects) and carry them in the swarm. They offer the been assessed, but as deforestation proceeds throughout prey to the nonhunting females as ‘‘nuptial gifts’’ to be the world, Diptera associated with this habitat will likely fed upon during mating. A few species have reversed be threatened. the trend of male-dominated swarms: instead, females Wetlands have been greatly reduced in many areas form the aggregation, which prey-bearing males visit of the world, in many instances for the express purpose to selectively mate with the most desirable individuals of eliminating biting fly vectors of disease. The loss of (such female-dominated swarms are also known for such habitats, however, also eliminates populations of some Phoridae). In some dance flies, the prey items other aquatic Diptera that have important ecological themselves have changed, with males presenting al- roles in the environment. ready fed-upon prey, inanimate objects such as plant Another group of Diptera whose conservation needs seeds, or even inedible bodily secretions. In these spe- are relatively well known is the endangered fauna cies, the giving of nuptial gifts apparently has become of Hawaii. There are several species of Drosophila ritualized, losing all of its functional basis. that have been proposed for listing as endangered species. Because of their poor public image, Diptera are usu- ally not considered flagship species for conservation IV. CONSERVATION BIOLOGY projects. In the southwestern United States, however, OF DIPTERA an endangered species of mydid fly has been used to spearhead efforts to halt the final destruction of an Because of the perception of almost all Diptera as dis- endangered habitat in the Los Angeles area. The Delhi ease-carrying filth flies, there is little public sympathy Sands Giant Flower-Loving Fly (Rhaphiomidas termina- or interest in their conservation. Also, most Diptera are tus abdominalis) is the largest and most identifiable of extremely poorly known, and the study of many families a number of threatened taxa that live in this habitat, 826 FLIES, GNATS, AND MOSQUITOES which is reduced to just a few acres in extent. The other Bibliography subspecies of this taxon, R. t. terminatus, previously went extinct when its habitat in the coastal dunes near Cumming, J. M. (1994). Sexual selection and the evolution of dance the Los Angeles International Airport was almost com- fly mating systems (Diptera: Empididae: Empidinae). Canadian Entomologist 126, 907–920. pletely destroyed by urbanization. Other species of Evenhuis, N. L. (1994). Catalogue of the Fossil Flies. Backhuys, Leiden. Rhaphiomidas are also considered endangered, as are Feener, D. H. Jr., and Brown, B. V. (1997). Diptera as parasitoids. other Diptera living in small, isolated, sandy habitats. Annual Review of Entomology 42, 73–97. In general, the conservation status of Diptera on a Ferrar, P. (1987). A guide to the breeding habits and immature stages worldwide scale is unknown. Undoubtedly many of Diptera Cyclorrhapha. Entomonograph 8, parts 1 & 2. E. J. Brill/Scandinavian Science Press. Leiden, Copenhagen. species are lost to deforestation, but only those in a McAlpine, J. F. (ed.) (1989). Manual of Nearctic Diptera, Volume 3. few well-known groups (like syrphids) or in habitats Agriculture Canada Monograph No. 32. that are of interest to some people (wetlands, sand McAlpine, J. F., and Munroe, D. D. (1968). Swarming of lonchaeid dunes) have been studied. The situation is unlikely to flies and other insects, with descriptions of four new species of change until we know much more about the systematics Lonchaeidae (Diptera). Canadian Enomologist 100, 1154–1178. Sivinski, J., Marshall, S., and Petersson, E. (1999). Kleptoparasitism of flies. and phoresy in the Diptera. Florida Entomologist 82, 179–197. Smith, K. G. V. (1989). An introduction to the immature stages of British flies: Diptera larvae, with notes on eggs, puparia and pupae. See Also the Following Articles Handbooks for the Identification of British Insects 10 (14). Yeates, D. K., and Wiegmann, B. M. (1999). Congruence and contro- BEETLES • BUTTERFLIES • HYMENOPTERA • INSECTS, versy: Toward a higher-level phylogeny of Diptera. Annual Review OVERVIEW • MOTHS of Entomology 44, 397–428.