Deer Fly

Chrysops, commonly known as deer flies, are robust, medium-sized flies belonging to the family Tabanidae. They range from 6-12 mm in length, characterized by their iridescent green or gold eyes (often with contrasting bands), dark bands on their wings, and a yellow or black body. Only the female deer fly bites, requiring a blood meal for egg development. Males feed on nectar. The lifecycle initiates with eggs laid in masses on vegetation overhanging water. Larvae are aquatic or semi-aquatic, developing in moist soil or mud along the edges of ponds, streams, or swamps. Larval development is lengthy, often taking one to two years and progressing through 6-11 instars, before pupation in drier soil for 1-3 weeks.

Deer flies are diurnal, with peak biting activity occurring on warm, sunny days, particularly from late morning to early afternoon. They are persistent and aggressive biters, often targeting the head and shoulders, and are attracted to large, dark, moving objects and carbon dioxide. Their flight is strong, direct, and often accompanied by an audible buzzing sound. Females actively pursue hosts, making them a significant nuisance in outdoor recreational areas. Foraging behavior is largely confined to areas near their aquatic breeding sites.