FIGURES 56-59 (56) Adult flower fly (Syrphidae: Eristalis sp.). (Photograph by R. F. Harwood.) (57) Rat-tailed maggot (Syrphidae). (Photograph by R. W. Merritt.) (58) Adult stalk-eyed fly (Diopsidae). (Photograph by R. D. Akre.) (59) Adult picture-winged fly (Otitidae: Melieria similies). (Photograph by J. A. Novak.)

FIGURES 56-59 (56) Adult flower fly (Syrphidae: Eristalis sp.). (Photograph by R. F. Harwood.) (57) Rat-tailed maggot (Syrphidae). (Photograph by R. W. Merritt.) (58) Adult stalk-eyed fly (Diopsidae). (Photograph by R. D. Akre.) (59) Adult picture-winged fly (Otitidae: Melieria similies). (Photograph by J. A. Novak.)

individuals are frequently found flying near flower heads where they obtain nectar. Adults are common near wetlands and lakes (e.g., Eristalis, Allograpta) but are also abundant in terrestrial areas (e.g., Merodon, Syrphus) where appropriate flowering vegetation grows. In aquatic habitats the larvae, or rat-tailed maggots, as they are called, are collector—gatherers and may use retractable siphons for respiration (Fig. 57). Emergent vegetation, or vegetation at the aquatic—terrestrial interface, may be infested with aphids and other homopterous herbivores that certain flower fly larvae devour upon discovery. Some aphids enter plant stems compromised by boring larvae of other orders (e.g., Lepidoptera) to feed on decaying plant juices; it is not uncommon to find flower fly larvae that have also entered the damaged areas of plants to obtain prey. Predatory habits are also seen in terrestrial habitats, where larvae of certain species will inhabit dung, rotting logs, and decaying vegetation, as well as the exterior of plants. Overall, larval habitats are diverse, including dung, rotting cactus, peat, and hymenopteran nests. Some species have also been implicated in intestinal myasis.

diopsidae The stalk-eyed flies (Fig. 58) are one of the most aptly named and morphologically unusual dipteran families (150 species). Each eye and its antenna are positioned at the end of individual stalks that protrude laterally from the head; the distance from eye to eye may be approximately equal to the entire body length! North America's one species (Sphaerocephala brevicornis) has very short eye stalks and breeds in decaying organic matter. The adults of this species exhibit no particular courtship displays, whereas highly adorned males of Afrotropical species (Diopsis) battle with one another using their stalks as levers during aggressive "wrestling matches." The larvae of Diopsis are herbivorous, and some species develop within the stems of rice plants.

otitidae These flies are also known as picture-winged flies because their boldly patterned wings are used in courtship and species recognition (Fig. 59). Adults are commonly found walking along vegetation flashing their wings. Otitids are abundant in both aquatic and terrestrial habitats (800 species). In marshes and vegetated lake margins, picture-winged flies are herbivores (Eumetopiella), secondary invaders of damaged plants (Chaetopsis), and general scavengers (Seioptera). Herbi-vory also occurs in terrestrial species (Tetanops, Tritoxa), but scavenging of decaying organic material appears to be more common (Delphinia, Euxestra, Notogramma). Some species also attack fungi (Pseudotephritis).

pyrgotidae Although some species of certain fly families (e.g., Tipulidae) are attracted to collecting lights at night, pyrgotid flies are unusual in that they are exclusively nocturnal. These flies (200 species) are relatively large and usually have strongly patterned wings (Fig. 60). Adults (e.g., Pyrgota, Sphecomyiella) seek scarab beetles, most notably June beetles, and apparently attack flying beetles by laying a single

FIGURES 60-63 (60) Adult of Pyrgotidae. (61) Adult marsh fly (Scromyzidae: Limnia). (62) Adult shore fly (Ephydridae: Ochthera mantis). (Photographs by The Cleveland Museum of Natural History.) (63) House fly adult (Muscidae: Musca domestica). (Photograph by R. W. Merritt.)

egg on the dorsum of the thorax or abdomen that is exposed when a beetle's elytra and wings are spread. The larva hatches from the egg and burrows into the body, acting as a parasitoid. The feeding larva eventually kills the host and consumes the remaining tissue. Larvae pupate within the hollowed host, and the adult exits the beetle exoskeleton to continue the life cycle.

tephritidae These true fruit flies (4000 species) are essentially entirely terrestrial in their habitat selection, although the host plants exploited by the family sometimes grow at the margins of lakes and marshes. Adults (Fig. 42) oviposit on the flower heads of the plant family Compositae or on fleshy fruits. Like the Otitidae, the wings of most adults are distinctly patterned, and adults flash their wings during courtship; this behavior has earned the Tephritidae a second common name, "peacock flies." Species tend to be fairly specific in their host plant preferences or at least attack a narrow spectrum of plant taxa. Fruit fly species are also specific in the area of a plant that they infest. Some species are frugivorous (Ceratitis, Rhagoletis), seed-head predators (Euaresta, Trupanea, Tephritis), gallmakers (Eurosta), or leafminers (Euleia). Frugivorous larvae damage the host fruit, causing it to rot quickly; seed predators of select young, developing seeds. Galls may be formed on a variety of plant areas, including stems, leaves, and flower heads.

dryomyzidae These are relatively uncommon flies (300 species), with the biology of only 2 of the 8 North American species known. Dryomyza anilis is a scavenger and breeds in decaying mammalian carcasses; it can be reared on raw ground beef. A contrasting life history is found in Oedoparena glauca, which preys on barnacles in the intertidal zone of western North American shorelines. This character makes O. glauca one of the truly marine insects, as it is tied intimately to an ocean-inhabiting invertebrate. Adults lay their eggs into the barnacle's operculum when dropping tide levels expose them. Larvae consume the soft tissue, and mature larvae frequently move to new barnacles to continue feeding. Pupariation occurs within the final host.

sepsidae The black scavenger flies are fairly abundant in both aquatic (Enicomira, Themira) and terrestrial (Sepsis) environments (250 species), where the larvae are scavengers of decaying organic matter. Dung of a variety of mammalian animals, carcasses, rotting snails, and washed-up seaweed have been exploited. The adults of many species are easily recognized by their rounded heads and the presence of a black dot at the apex of each wing.

sciomyzidae Called marsh flies and snail-killing flies, neither name encompasses all the habits of this well-studied family (500 species). Some species (e.g., Dictya, Limnia) are found in marshes, but some species of certain genera (e.g., Sciomyza, Pherbellia) are fully terrestrial. Many species are larval parasitoids or predators of snails, and some attack slugs (e.g., certain Tetanocera, Euthycera) or fingernail clams (Renocera); the larvae of one genus (Antichaeta) prey on the eggs of aquatic and semiaquatic snails. The adults range in color from yellowish brown to brownish black, have antennae that may be long or short, and vary in size from a few millimeters to nearly 1 cm (Fig. 61). However, the trophic niche of exploiting freshwater or terrestrial Mollusca (i.e., snails, slugs, and clams) ties all Sciomyzidae together evolutionarily. Ovipositional habits vary from certain species that lay their eggs directly on the host (e.g., Sciomyza) to species that lay eggs on plants, thus requiring larvae to search for their hosts (e.g., Tetanocera). Only one species (Sepedonella nana) from Africa seems to deviate from the trophic tie to mollusks, as laboratory-reared larvae have fed and survived on aquatic oligochaetes in the laboratory.

chamaemyiidae Aphid flies are predators of aphids, mealy bugs, and other homopterous herbivores (250 species). Adults lay their eggs on plant surfaces, in galls, or in the egg sacs of scale insects, and the maggots can reduce homopteran populations (Leucopis). One report from Mexico showed that the adults of an aphid fly fed on the secretions of vertebrate animals and that the larvae may have developed in bird nests (Paraleucopis). Some taxa are found within emergent and shoreline vegetation of aquatic habitats, whereas others are encountered in woodland or open fields.

piophilidae These flies (70 species) are most commonly represented by the cheese-skipper fly (Piophila casei), a cosmopolitan consumer of proteinaceous materials. Larvae frequently infest cheese and exhibit the rather peculiar escape strategy of grabbing the posterior body segment with their mouth hooks to form a U shape and then releasing their grip, which causes the larvae to propel, or skip, away from their original location. These behaviors give them the name cheese-skipper, even though the larvae are also known to consume the drying tissues of aging mammalian carcasses and dung. While most species appear to be scavengers of decaying materials and carcasses (Protopiophila) or mushrooms (Amphipogon), the larvae of some species are parasitic on avians (Neottiophilum).

sphaeroceridae The small dung flies represent a speciose family (2500 species) that have predominantly scavenging larval feeding habits. One genus (Leptocera) consistently appears to be scavengers; however, the spatial niches inhabited by the larvae are highly diverse. Larvae have been found in decaying vegetable matter, sewage, dung, dung beetle broods, stranded masses of seaweed, fungi, slime molds, carrion, and the organic matter accumulated within cups of bromeliads. Muddy, organic-rich margins of aquatic habitats, such as marshes and ponds, will support virtual clouds of adults. Some species are quite habitat-specific, such as those that inhabit bogs. The adults of common species have long, stiff bristles dorsally and are black to gray in color, and the arista is several times longer than the other segments of the antenna.

ephydridae These flies are also known as shore flies, and most taxa are associated with aquatic habitats. This is one of the most genera-rich families of Diptera (1300 species) and one of the most diverse in feeding habits. Larvae are consumers of decaying organic matter (e.g., Discocerina), secondary stem borers of damaged plants (e.g., Typopsilopa), primary herbivores (e.g., Hydrellia), generalist feeders of algae (e.g., Scatella), specialist consumers of algae and cyanophytes (e.g., Hyadina), diatom specialists (e.g., Parydra), predators (e.g., Ochthera), and consumers of spider eggs (Trimerina). Virtually all aquatic habitats, from flowing water to stagnant environments, temporary to permanent, fresh water to hypersaline, and cold water to hot springs, are occupied by ephydrids. Terrestrial environments are less likely to support ephydrid populations, but these flies are found in moist woodlands and even in sod from suburban areas. Shore flies can be abundant in human-made habitats, including constructed wetlands and sewage treatment plants. It is difficult to make generalizations about the overall morphology of this family, except that the adults tend to be small; the smallest adults (Lemnaphila), only a couple of millimeters across, mine the thalli of duckweed plants. Adult body color ranges from silvery gray to jet black, and the wings are completely colorless to highly patterned with various shades of gray and brown (Fig. 62). The species, habitat, and feeding diversity have led the dipterist Harold Oldroyd to state that the shore flies are currently "in the flower of their evolution."

drosophilidae Pomace flies, vinegar flies, and small fruit flies are another highly species-rich family (3000 species). The latter name has led to some confusion as the Tephritidae are also known as fruit flies. The adults (Fig. 44) are small (generally only a few millimeters in length), but can disperse about 10 km in 1 day. Some drosophilids are frugivorous, but a vast array of food sources are used. For example, many feed on fungi (e.g., Amiota, Mycodrosophila, Stegana, Scaptomyza), living flowers (e.g., Apenthecia, Styloptera) or are predaceous on other invertebrates (e.g., Rhinoleucophenga, Cacoxenus, Acletoxenus). Indeed, the genus Drosophila, mostly known for the experimental studies of D. melanogaster, in the wild exhibits a vast trophic ecology and includes species that develop in rotting vegetation, rotting fruit, tree sap, fungi, living flowers, and plant stems and that prey on other invertebrates. Two Drosophila species are commensal with crabs: larvae live attached to the crab exoskeleton and consume semiliquid excretions from the crab or develop in the crab's branchial chamber and consume its microflora.

chloropidae Flies is this family are called chloropid flies or frit flies (2000 species). Larvae are generally scavengers of decaying organic matter, secondary invaders of damaged plants, or primary herbivores. Adults are common and abundant among vegetation in terrestrial and aquatic situations. Species have been reared from dozens of different substrates around the world. Grasslands commonly support populations of certain genera (e.g., Meromyza, Parectecephala), and fungi are the sole food of others (e.g., Fiebrigella, Apotropina). However, a great diversity occurs in vegetated areas of aquatic habitats (e.g., Chlorops, Epichlorops, Eribolus, Diplotoxa) where most taxa are detritivores in decaying masses of vegetation, secondary stem borers, and primary herbivores of aquatic or semiaquatic plants. A few taxa are predatory on Homoptera (e.g., Thaumatomyia). Other, less common, larval food sources include dung (Cadrema), decaying wood, and bird nest debris (Gaurax), and one Australian genus (Batrachomyia) is subcutaneously parasitic on frogs and toads. The adults tend to have rounded flagellomeres and range from dull colored to bright yellow or green, and many species have a distinctly shiny triangle positioned at the vertex of the head.

agromyzidae These are known as the leaf-miner flies because of their highly herbivorous nature. Like the Chloropidae, agromyzids are well represented in both aquatic and terrestrial environments (2000 species). Herbaceous and woody plants are both attacked, but larvae tend to feed on a single host plant, or a narrow spectrum as host plants as leaf miners, stem borers, or seed head predators. Wetland taxa can form large populations in which both monocot and dicot flora are used as host plants (e.g., Agromyza, Cerodontha, Liriomyza, Phytomyza). One species (Melanagromyza dianthereae) is a specialist stem borer of water willow, a flowering plant found at the edge of streams. The females of this fly lay eggs on the exterior of the plant, and upon hatching the larvae burrow into the stem to initiate feeding. Leaf mines are frequently seen as dead or brown areas on a leaf surface, and mine morphology is sometimes distinctive enough to determine which agromyzid species is responsible for plant damage.

anthomyzidae These common flies are an example about which little is known of their biology (50 species). One genus (Anthomyza) has small yellowish adults that may feed on the culms of wetland sedges, but it is unclear if they are herbivorous or act as secondary stem borers after plants have been attacked by other herbivorous insects.

muscidae This large family (4000 species) includes anthropophilic species such as the house fly (Musca domestica) (Fig. 63) and the stable fly (Stomoxys calcitrans) (Fig. 32). The house fly is well known for its "filthy habits," and the stable fly bites both humans and livestock. The reproductive rate of the house fly is noteworthy, as one female can eventually give rise to 2 billion other female flies after several summer generations are produced (assuming all flies live, which is never the case). A short life cyle (12—14 days required for development from egg to adult in summer temperatures) is at least partially responsible for the success of this species and is necessary for developing in such ephemeral, human-made habitats such as dung heaps, garbage cans, and mammalian road kill. However, most muscid species are not directly associated with human populations. The larval feeding habits found among the Muscidae include herbivory (Atherigona, Dichaetomyia), scavenging (Graphomyia), and predatory behaviors (Coenosia, Lispe, Spilogona). A few taxa cause myiasis in birds (Muscina) or are avian blood feeders (Philornis). Some Muscidae form a cocoon prior to pupariation (formation of puparia), which is uncommon among Diptera. Adult muscid flies may be predaceous on other insects, but most are generalized scavengers or feed on pollen.

oestridae These are commonly known as bot or warble flies (40 species). The larvae of all species are endoparasites. Species that attack livestock burrow into the host skin to feed on living tissue and either form their pupae under the skin, forming warbles (Hypoderma), or drop off the host and pupariate in soil (Oestris). Four species of the horse bot fly (Gasterophilus) infest the alimentary tract of horses (Fig. 38), donkeys, and mules. One genus (Cuterebra) (Fig. 64) infests lagomorphs and rodents and is among the biggest bot flies (about 2.5 cm). The human bot fly (Dermatobia) lays eggs on mosquitoes and other biting flies. When a larva hatches, it hangs onto the bloodsucker's leg until it lands on a human to take obtain a blood meal. The maggot then drops onto the host and burrows into the skin. Human bot flies are restricted to the Neotropical areas of the world and use a variety of mammalian hosts in addition to humans. North American vacationers and

FIGURE 64-65 (64) Adult rodent bot fly (Oestridae: Cuterebra jellisoni). (Photograph by C. Baird and R. D. Akre.) (65) Adult of Tachinidae. (Photograph by E. A. Elsner.)

workers visiting the fly's home range frequently return home with a painful welt, under which lays a feeding maggot that respires through a small hole in the person's skin. The experience is painful, and most infected travelers have the larva removed surgically prior to pupariation or adult emergence.

nycteribiidae Bat flies (250 species) are specialized ectoparasites of bats. The spider-like adults lack wings, which probably reduces the host's chances of removing the fly. Females bear mature living young (i.e., they are pupiparous), which is uncommon among Diptera. Larvae receive nutrients produced by glands within the female abdomen. The female bat flies deposit the larva on the walls of bat roosts, and females of some species will sit on top of the larva and briefly press it to the wall to ensure good adhesion. Pupariation occurs quickly without larval feeding. The adult emerges, and then seeks a host to continue the bloodsucking habit. Therefore, larval feeding does not occur outside of the adult female fly.

calliphoridae The blow flies are thought to have been given their name from Homer's classic book, The Iliad, in which he wrote about the "blows of flies" infesting the wounds of injured and dead soldiers. Most of the 1000 species of this cosmopolitan family are attracted to rotting flesh and can sense the chemical scent of decay within minutes of death. In nature, the adults accelerate the decomposition of all types of vertebrate carcasses, and most blow flies (e.g., Calliphora, Cochliomyia, Lucillia, Phaenicia) are specialist scavengers. Because of the ability to find dead bodies rapidly, forensic scientists use the stage of larval development (i.e., age of a larva) found on corpses of people who died from suspicious causes as a way to determine the time between death and corpse discovery. It is well documented that by using this method, the time of death often can be estimated with a fair amount of accuracy. Other taxa of blow fly, however, exhibit other feeding habits, such as parasitism of land snails (Helicobosca), earthworms (Pollenia), and amphibians (Bufolucilia). The adults are also known as blue bottle and green bottle flies because some taxa have metallic brightly colored bodies (Figs. 35 and 37).

sarcophagidae Flesh flies have been given a name that often contrasts their biology. Only a few of the 2500 species invade or consume carrion (Sarcophaga) or living tissue (Wohlfahrtia). Dung (e.g., Ravinia) is more commonly used. Many taxa are parasitic on other invertebrates (snails, earthworms, insects, and others), whereas some specialize in consuming the decaying bodies of insects found in the bottoms of pitcher plants of wetland habitats. Females are viviparous, young hatch within the female's abdomen, and she deposits them as first instars on the desired substrate. This may give flesh flies an advantage over potential competitors for food because mortality of eggs by predation or parasitism is avoided, and larvae can feed immediately rather than waiting to hatch for some days prior to feeding.

The adults of most genera are easily recognizable by the gray thorax possessing longitudinal black stripes (Fig. 36).

rhinophoridae This is an unusual fly family in that nearly all of the 100 species for which biological details are known are specialist endoparasitoids of terrestrial isopods (also known as sow bugs, pill bugs, and potato bugs). This family represents the only dipterans that attack isopods. The larval life is tenuous, because larvae hatch from eggs laid in moist soil and must wait for a passing isopod. Perhaps the proleg-like apparatus present on the first instar is an adaptation to securing itself to a host. Both species of rhinophorids found in North America were probably introduced from Europe.

tachinidae These flies (9500 species) (Fig. 65) are important parasites of a variety of other insects and are used in biological control programs against pestiferous Lepidoptera. Eggs are deposited on hosts or in areas where hosts are common. Some species retain their eggs so that they will hatch almost immediately after being laid; this strategy prevents the loss of the egg if the host happens to molt shortly after oviposition. Insertion of the egg through the epidermis of the host has evolved in a few species (Phorocera). An alternative strategy used by some taxa is to lay many eggs on partially consumed plants; when a potential host returns to continue feeding, the eggs are consumed along with the plant material. A few eggs survive maceration by the mandibles, and the larvae hatch within the host's foregut. Other genera broadcast their eggs, and the larvae burrow selectively into soil or rotting wood where they actively seek a host insect. Most often, tachinid flies attack only one species or a narrow spectrum of hosts; however, a small number (Compsilura) have been reared from some 200 different animal host species.

See Also the Following Articles

Drosophila melanogaster • House Fly • Mosquitoes • Tsetse Fly Further Reading

Brown, B. V. (2001). Flies, gnats, and mosquitoes. In "Encylopedia of Biodiversity" (S. A. Levin, ed.), pp. 815—826. Academic Press, London. Cole, F. R. (with collaboration of E. I. Schlinger) (1969). "The Flies of

Western North America." University of California Press, Berkeley. Courtney, G. W., Teskey, H. J., Merritt, R. W., and Foote, B. A. (1996). Aquatic Diptera, Part One, Larvae of aquatic Diptera. In "An Introduction to the Aquatic Insects of North America." (R. W. Merritt and K. W. Cummins, eds.), pp. 484-514. Kendall-Hunt, Dubuque, IA. Dethier, V. G. (1963). "To Know a Fly." McGraw-Hill, Columbus, OH. Feener, D. H., Jr., and Brown, B. V. (1997). Diptera as parasitoids. Annu.

Rev. Entomol. 42, 73-97. Hennig, W. (1973). Diptera (Zweiflügler). In "Arthropoda," Hälfte 2, "Insecta," No. 2, "Spezielles, 31," (Helmecke et al, eds.), Vol. IV of "Handbuch der Zoologie: Eine Naturgeschichte der Stämme des Tierreiches." Berlin/New York. James, M. T. (1948). "The Flies That Cause Myiasis in Man." U.S.

Department of Agriculture, Washington, DC. [Publication No. 631] McAlpine, J. F., Peterson, B. V., Shewell, G. E., Teskey, H. J., Vockeroth, J. R., and Wood, D. M. (coordinators) (1981). "Manual of Nearctic Diptera," Vol. 1. Research Branch, Agricultural Canada. [Monograph 27]

McAlpine, J. F., Peterson, B. V., Shewell, G. E., Teskey, H. J., Vockeroth, J. R., and Wood, D. M. (coordinators) (1987). "Manual of Nearctic Diptera," Vol. 2. Research Branch, Agricultural Canada. [Monograph 28] McAlpine, J. F., and Wood, D. M. (coordinators). "Manual of Nearctic Diptera," Vol. 3. Research Branch, Agricultural Canada. [Monograph 32] Merritt, R. W., and Cummins, K. W. (1996). "An Introduction to the

Aquatic Insects of North America." Kendall—Hunt, Dubuque, IA. Merritt, R. W., Webb, D. W., and Schlinger, E. I. (1996). Aquatic Diptera, Part Two, Pupae and adults of aquatic Diptera. In "An Introduction to the Aquatic Insects of North America" (R. W. Merritt, and K. W. Cummins, eds.), pp. 515—548. Kendall—Hunt, Dubuque, IA. Oldroyd, H. (1964). "The Natural History of Flies." Norton, New York. Oosterbroek, P., and Courtney, G. W. (1995). Phylogeny of the nema-tocerous families of Diptera (Insecta). Zool. J. Linn. Soc. 115, 267—311. Papp, L., and Darvas, B. (eds.) (2000). "Manual of Palaearctic Diptera," Vol.

1. Science Herald, Budapest. Yeates, D. K., and Wiegmann, B. M. (1999). Congruence and controversy: Toward a higher-level phylogeny of Diptera. Annu. Rev. Entomol. 44, 397-428.

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