Yellow Flies

Yellow flies are biting flies. Like the common mosquito, females feed on blood to get nutrition for egg production. Both male and female yellow flies eat plant nectar and pollen for energy. Males do not bite. Yellow flies are found extensively throughout Latin America and tropical regions of the United States. Although a number of flies are referred to as yellow flies, the Diachlorus ferrugatus is the true yellow fly and is believed to have migrated into the United States through Mexico.

Although yellow flies prefer hot, humid weather are most active during the afternoon hours just before twilight. They are also attracted to water, where they lay their eggs, and are frequently found at the edges of forest lakes and streams.

Adults measure approximately 1 cm in length, with one pair of black front legs and two pair of yellow back legs. Their abdomens are yellow and furry. Yellow fly eggs measure approximately 1.5 mm. Initially white, these eggs quickly darken and turn black, at which point they are commonly mistaken for feces. Larvae are semiaquatic, feeding on decaying organic matter found on water banks. They molt approximately 10 times before burrowing into the ground for winter. After emerging, they locate a dry location within which to pupate.

Female yellow flies are fierce biters. Traps may help reduce populations near gardens or swimming pools. However, in case of a large populations, contact your local pest control professional for a consultation and solutions.