The Black Dump Fly: A larval predator of house flies

The black dump fly ( Figure 1 ) is a shiny, black fly similar in size and appearance to the house fly. It is currently regaining popularity as a biological control agent for controlling house flies on poultry farms without the use of pesticides. The fly is native to the U.S., and Central and South America. The current scientific name of the fly is Hydrotaea aenescens, however it is sometimes referred to by its former name, Ophyra aenescens. The purpose of this document is to provide some general information about this fly, its biology and behavior, and how it is being used to control house flies in animal manures. Biology Although the black dump fly is referred to as a biological control agent for house flies, it is the larvae (or maggots) that are actually the predators. Black dump fly larvae will kill the larvae of many (but not all) other fly species. When fly larvae that are suitable dump fly prey are in a substrate with dump fly larvae, it is generally only the dump fly larvae that survive to become adults. But black dump fly larvae do not need to feed on other fly larvae to develop normally; they can develop using only the nutrients in the substrate. For this reason they are called facultative predators. Black dump fly larvae have the ability to kill up to 20 house fly larvae daily during much of their developmental period. This is a rare example of animals killing more prey than they can eat. When black dump fly larvae and house fly larvae are together in the same substrate, the dump fly larvae will pursue and kill the house fly larvae. When a house fly larva is killed, nearby house fly larvae are attracted. This activity makes it easier for dump fly larvae to eliminate their victims. The black dump fly has a life cycle similar to that of the house fly. Females lay an average of 170 eggs over a period of 7 to 10 days. Under optimum conditions (80° F or 26.7 °C, and 60% RH), eggs hatch in 18 to 24 hours. There are three larval or maggot stages, followed by the pupal stage where the larva changes to the adult fly. Adults emerge from their pupal case, and mate after about 5 days. About 2 days later, females begin laying their eggs. Time required from egg to adult is approximately 14 days. This cycle may be shorter at warmer temperatures, and longer at cooler temperatures