Adult house flies are usually gray or black and can be distinguished by the four black lines running across their thorax. Adults measure 4 – 8mm in length and have hair-like projections covering most of their bodies. Typically, females are larger than males but both have red, compound eyes and sponging-sucking mouths used to eat liquid and saliva-dissolved food stuffs. House flies are active during the day and will hide or rest in high places to avoid detection and threats.
House flies eggs are typically laid amongst larval food sources and hatch within a day. Known as maggots, the fly larvae are pale white, 3 – 9mm long and legless. After 14 – 36 hours, maggots will move to a cool, dry spot and transform into reddish-brown pupae from which adults wills then emerge. Females can mate as soon as 36 hours after emerging from the pupae.