These small flies are often robust. Their wings in many cases have a yellow tinge, and sometimes boast dark spots. The head is “nearly twice as wide as long, in profile more or less oval, higher than long.” The postocellar bristles converge. Usually the tibiae have “preapical dorsal seta” though this is occasionally lacking on the rear tibiae. The abdomen appears soft and plump (Shewell, in McAlpine, 1987).
Females are oviparous. The larvae are white, at least partly translucent, and in shape “cylindroconical.” The pupae are “usually covered with calcereous deposit expelled as liquid from larval anus” at the time of pupation (Shewell, in McAlpine, 1987).
Oldroyd (1964) reports that the larvae develop in leaf mold and other decaying plant material. Some more specialized species have leaf-miner or gall-maker larvae. In some species the larvae develop in bird nests.
Shewell notes that Lauxaniid flies are found on all the continents save Antarctica, and that many Pacific islands are home to species found nowhere else on earth (Shewell, in McAlpine, 1987). Unfortunately for those of us who try to understand Dipteran taxonomy, Shewell quotes Stuckenberg as saying “the Neotropical fauna has little in common with that of the Old World.”
In the cool weather of late fall and of early spring, Heleomyzid flies may be the only adult flies to be seen in West Virginia. On the other hand, go looking for adult flies of this family in July and you will likely be disappointed, as this is a fly of cool conditions.
A majority of Heleomyzid flies are colored yellow, orange, or brown. Their wings are often tinted with yellow to amber color, are sometimes spotted, and the costa usually has spines. The antennae are small and do not point forward. Vibrissae are present, and postvertical bristles are present and converging (Borror and White, 1970).
In Canada and the United States are some 135 species of Heleomyzid flies. The larvae of some species live in leaf mold or in other decaying vegetation, while a few are bird nest specialists or leaf miners (Arnett, 2000).
Winthemia cf. quadripustulata
Length: typically 7 mm
Older works put genus Winthemia in subfamily Goniinae.
Winthemia is a common and widespread genus. Its life history includes the parasitizing of caterpillars. Among the hosts of various Winthemia species are Cecropia Moth larvae, Tobacco and Tomato Hornworms, Fall Armyworm, Corn Earworm, and Green Cloverworm.
Other reported hosts include Weevils and Wasps (Arnaud, 1978).
Winthemia has recumbent hairs on the third and fourth abdominal tergites.
DeLoach and Rabb (1971) described the life history of one Winthemia species, Winthemia maducae, emphasizing its parasitizing of the Tobacco Hornworm, Manduca sexta. The female flies laid an average of eight eggs on final instar caterpillars. Hatching of the eggs seemed not tied to a particular number of days, but rather coincided (by an unknown mechanism) with the host’s prepupa molting, “at which time the parasitic larvae entered the host pupa before its integument hardened.”
The fly larvae developed within the hornworm pupa for seven days, then exited the pupa and underwent its own pupation within two days, typically in the upper several inches of soil. The pupal period averaged sixteen days, with the females typically emerging after the males. Oviposition was observed four days after the adult’s emergence. The overall development took about 37 days. The authors noted that while the sex ratio in the laboratory was equal, in the field the researchers found only females, suggesting that the males may live most of their lives in a different habitat from the females.