They are cylindrical and taper anteriorly. Puparia are reddish brown and 4 - 7 mm long. The respiratory horns found along the posterior border of the 4th segment are small but visible, and are darkened basally. House flies are common on animals in confined rearing facilities and other buildings. Adults do not bite but annoy animals by congregating around orifices, wounds, and soiled regions.
Females lay eggs in moist decaying organic matter, such as manure, garbage, silage, and food wastes.
Larvae complete development and pass through 3 instars usually within one week to 10 days. They spend a further week to 10 days as puparia before emerging as adults. At 25 degrees Celsius, the entire life cycle from egg to adult is completed in 14 to 18 days. Several generations occur during the course of the summer and breeding may continue throughout the year in warm buildings. In unprotected breeding sites house flies overwinter as larvae or puparia.