Chironomidae Chironomid Midges

Adult chironomid midges (Fig. 8.11 A) are 1 —10 mm long, with slender legs, narrow, scaleless wings, and plumose antennae in the adult males. They are often mistaken for adult mosquitoes but lack the long proboscis and are unable to feed on blood. Adults are short-lived, living only a few days to several weeks. Some imbibe ho-neydew and other natural sugars, but some take no food at all as adults. Most chironomid larvae are aquatic or semiaquatic and construct tubes in, or attached to, the substrate. They are often the most abundant benthic organisms and occur in all types of habitats, including rivers,

FIGURE 8.11 Chironomidae. (A) Adult male (Chironomus sp.); (B) larva (Pseudodiamesa sp.). (From McCafiferty, 1981.)

streams, lakes, ponds, water supplies, and sewage systems. Chironomid larvae are cylindrical and have paired prolegs on the prothorack and last abdominal segments (Fig. 8.1 IB). The head is heavily sclerotized and nonretractile. They have no spiracles. Many species, however, have a hemoglobin-like substance in their hemolymph and are called bloodworms because of their pink or red color. Most species are detritus feeders that graze on aquatic substrates. Others filter drifting food particles from the water with strands of saliva or are predators on other chironomid larvae or oligochaete worms.

In addition to being mistaken for adult mosquitoes, chironomids can pose other medical and economic problems. Inhabitants of localities where large, synchronous emergences occur can develop allergies to the larval hemoglobin that is carried over from the larva to the adult and becomes airborne as the bodies of the adults decompose (Cranston, 1988), Larval hemoglobin also can induce allergies in workers who process bloodworms into fish food for aquaria. Large chironomid emergences from

Adult phorids are 0.5—5,5 mm long with an enlarged thorax, giving them their characteristic humpbacked appearance (Fig. 8.15A and 8.15B). The hind femora are flattened, and the major bristles of the head and legs are feathered, They rtm in short, quick bursts and are usually found in damp places near larval habitats, Larvae (Fig. 8.15C) are less than 10 mm long, lack an apparent head, and possess abdominal projections that range from being inconspicuous to large and plumose. Larval habitats are extremely varied. They include all kinds of decomposing plant and animal matter, fungi, bird nests, feces, dead insects, sewage treatment beds, and commercial mushrooms. Some larvae are internal parasitoids of other arthropods or live as commensals with social insects.

Megaselia scctlaris (Fig. 8.15B) is the phorid of most medical importance. The female lays eggs in fruits and vegetables, feces, and decaying plant and animal matter. Sporadic cases of facultative human myiasis caused by M. scalaris have been documented in many areas of the world; they include cutaneous, pneumonic, nasal, gastrointestinal, urogenital, and ophthalmic myiasis (Carpenter and Chastain, 1992). Phorid larvae also are commonly associated with decomposing animal remains, where they tend to be late invaders after the calliphorid flies have pupated (Smith, 1986). This fly is often a problem around mausoleums and mortuaries, where the larvae develop in burial crypts, producing large numbers of adults (Katz, 1987). A small, black, European species called the coffin fly (Conicem tibialis) (Fig. 8.15A) is commonly associated with interred human remains that have been underground for a year (Smith, 1986).

There are ca. 350 species and 48 genera of phorid flies in North America. Keys to adults in the Nearctic region are provided in Peterson (1987). The biology, ecology, and keys for identification of Phoridae are compiled in Disney (1994).

Adults of this family vary in length from 4 to 25 mm and are distinguished by the presence of a spurious vein between the radius and media. Many are boldly marked with black and yellow transverse bands and are effective wasp mimics. Others, including Eristalis and Eristalinus, which are called drone flies, are covered with fine yellow hairs and resemble honey bees or bumble bees (Fig. 8.16A). Most adults are strong fliers and are often seen hovering near flowers, where they feed on nectar. They neither bite nor are capable of stinging. Syrphid larvae

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