The second instar is about 3 mm long at first and has a little more black coloration. When mature, the larva has a 5 to 8 mm long, light brown body with an entirely black head. Little house flies and coastal flies occur throughout this country, and both species are common in homes, barns, stables, and poultry houses in spring and fall. Larvae typically consume decaying organic matter and excrement but have been known to parasitize the intestinal tract of man and animals. In some areas, lesser house fly larvae are the predominant maggots breeding in chicken manure.
Flies are primarily an annoyance.
Like common house flies, little house flies breed in garbage and manure and may transfer disease-causing organisms to human food such as dysentery bacilli. The coastal fly, however, has not been implicated as a disease vector or an agent of myiasis. In mild climates, this species may overwinter as larvae, prepupae, or pupae. During severe winters, however, only pupae survive. Overwintering adults often become active by late February, but emergence of new flies from overwintering pupae usually does not occur before mid-March.