Deer Flies, Yellow Flies, and Horse Flies: Parkland Westin and Wellington
The family Tabanidae, commonly known as horse flies and deer flies, contains pests of cattle, horses, and humans. In Florida there are 35 species of Tabanidae that are considered economically important. Horse flies are known in Florida as a fierce biter. Like mosquitoes, it is the female fly that is responsible for inflicting a bite. The males are mainly pollen and nectar feeders. Tabanids are most likely encountered in hot summer and early fall weather. They are active during daylight hours.
Florida produces a large population of tabanids because of the availability of suitable habitat. Florida’s mild climate and large, permanently wet and undeveloped areas provide good breeding areas.
Eggs are laid in masses ranging from 100 to 1000 eggs. Eggs are laid in layers on a vertical surface, such as overhanging foliage, projecting rocks, sticks, and aquatic vegetation. Aquatic vegetation is preferred. A shiny or chalky secretion, which aids in water protection, often covers eggs. The vertical surfaces on which the eggs are deposited are always directly over water and wet ground favorable to the development of larvae. The female will not deposit egg masses on vegetation that is too dense. Eggs are initially a creamy white color but soon darken to gray and black. Eggs hatch in five to seven days, depending upon ambient weather conditions, and the larvae fall to the moist soil and water below.
Adult tabanids are encountered in Florida between the months of May and September. Most species overwinter in the larval stage and pupate during the spring and early summer. An egg mass has been found as early as May 5 and as late October 13. Most have a year-long life cycle, but some larger species may take two or three years. Adult life span is 30 to 60 days.
Currently there are no adequate means for managing populations. Traps are sometimes effective in small areas such as yards, camping sites, and swimming pools. Trapping of nuisance flies has reduced their numbers on the Atlantic Coast of the United States. Traps have been effective when used around cattle that are confined to manageable areas.
Some traps are black and shiny balls. The flies are attracted to these objects as the wind moves them. Malaise traps can catch large numbers of flies by simply being in their flight paths or by the use of attractants, such as CO2 and octenol. These traps are mostly useful for sampling. For personal protection, long sleeve shirts and pants in combination with a repellent containing diethyltoluamide (DEET), citronella, or geraniol are effective. For livestock, pyrethroid pour-ons function as limited repellents. Self-application methods are not effective for horse flies. Ear tags and head collars impregnated with insecticides have had success in control. For removal trapping, recent research has shown that blue cylinders (inverted cups, for example) coated with sticky material and attached to slow moving (<7 mi/hr) objects (e.g., the front of a truck or riding lawnmower) or on top of a cap worn atop a person’s head are effective at reducing the abundance of these flies.
Jason Squitier, University of Florida