There are 91 species in what is called the Drosophila repleta “group” in North and South America and they are native to this Hemisphere. Given the sudden and recent appearance of these flies in North America they may be native to Central and South America.
These little flies, closely related to vinegar flies or the “red-eyed” fruit flies, began to emerge as an issue around the year 2000, and now are often the dominant small fly pest indoors. There are several species with this name and their larvae will feed in sources of both vinegar flies and phorid flies – very wet areas with a buildup of organic sludge as well as in fermenting fruit and vegetable materials. Any place water can settle and allow buildup of organic matter can provide food resources, including floor drains, under and around broken tiles and loose flooring, along edges of floors, etc. The adult flies tend to spend much of their time resting on the walls and other surfaces. A life cycle from egg to adult can be completed in only 1 week.
These flies are very small, about 1/8 inch long, and with dark brown to black bodies and very dark colored eyes. Lighter colored spots over the thorax create a “freckled” appearance. They are slightly larger than the common vinegar flies with red eyes. The light colored larva is legless and very small and tapers to narrower ends at both front and back of the body. The pupa is distinctive with a pair of “horns” pointing forward at the anterior end.
Characteristicts Important to Control:
Cleaning is vital to control of these flies. An inspection is needed to identify the unsanitary condition that provides the food resource for the larvae and removal of the organic material will remove larvae and prevent repeat infestation. Flooring and other materials in poor condition need to be repaired. The use of biological cleaners can remove organic buildup in drains and other places. The inspection must include all food service and preparation equipment in restaurants, including drink dispensers, salad bars, and other equipment where moisture is present and may be trapped in tubes, gaps, or holes. Restrooms should also be carefully inspected and treated as needed to eliminate buildup of filth. If necessary, a light mist of pyrethrum can kill adult flies, but control of their source must be done as well. Fruit fly traps can be effective for monitoring for the adult flies.