Usually known genera of these "blowflies" are Lucilia and Calliphora, which develop mainly in decaying flesh. However, there are several species that are predaceous as adults on other insects. The food habits of the genus Bengalia were noted by Bequeart (1922). Adults of B. obscuripennis Bigot capture and feed on winged termites; B. jijuna F. and B. depressa Wlk. rob ants carrying larvae and pupae, to feed on these immature stages. Other species may rob ants of insect prey that re being transported to the nest.
Diverging from the usual habit of the family is Stomorhina lunata F., which is predaceous in the egg capsules of Locustana pardalina Wlk. Ptogieter (1929) observed in South Africa that 50-90% of the egg masses were destroyed by the maggots, and as many as 50 eggs of the predator were found in a single egg capsule. The flies are very active at the time of host oviposition. As soon as one of the hosts withdraws its abdomen from the ground, the flies rush to the spot to lay their eggs in the still fluid covering of the egg mass. Oviposition also occurs in partly hatched egg capsules. The partially grown larvae were observed to migrated from one capsule to another to feed. usually 2-3 puparia are found in an egg capsule, although sometimes the number may be 12. The life cycle probably takes less than one month in summer. In East Africa, 20% of the egg masses of Schistocerca gregaria F. were found infested during an outbreak following a 10-yr period of absence. Because of this, the species was presumed to have an unknown native host.
Several species are known to be parasitic on non insect hosts. The cluster fly, Pollenia rudis F. is an internal parasitoid of Allolophora and other earthworms. Keilin (1911b, 1915) and Webb & Hutchinson (1916) described the immature stages. Eggs are laid singly in crevices in the soil, hatching in 3 days. First instar larvae are very active and may enter the host body either through a natural orifice or through the body wall (De Coursey 1932). The posterior end of the body remains embedded in the aperture, allowing direct respiration. Egg, larval and pupal stages take 3, 13-11 and 11-14 days, respectively. One to 4 individuals may develop in each host. The life history and behavior of Onesia accepta Malloch, parasitic in Microscolex and other earthworms in Australia were discussed by Fuller (1933). Live larvae are laid, rather than eggs, and females were found to contain 500 or more eggs in various stages of development. The larvae were laid in soil, but the manner of their entry into the host was not found. In early stages, the larvae are found just beneath the skin, and parasitized earthworms may be recognized by constrictions of the skin along the path followed by the larva, this being regularly in spiral form about the body. Third instar larvae enter the body cavity, often killing the worm at this time and completing feeding as a scavenger. The duration of different stages is close to that for Pollenia.
Melinda cognata Meig. develops as an internal parasitoid in the snail, Helicella virgata Da Costa. Eggs were found in the mantle cavity and oviposition probably occurs while the hosts are copulating (Keilin 1919). The young larva bores its way into the kidney where it lies with its posterior end protruding into the mantle or the pulmonary cavity. The host dies when the parasitoid larva is in its early 3rd stage, and parasitoid pupation occurs within the host shell. The life cycle is ca. 15 days.