Tabanus nigrovittatus, also known as the greenhead horse fly, salt marsh greenhead, or simply the greenhead fly, greenhead or greenfly,[1] [2] is a species of horse-fly commonly found around the coastal marshes and wetlands of the Eastern United States. They are smaller than most horsefly species, instead being close in size to a common housefly. The biting females are a considerable pest to both humans and animals while they seek a source of blood protein to produce additional eggs:[3] greenhead larvae develop in the mud of salt marshes, and adult flies mate and lay their first group of eggs in the marsh, but to lay more eggs a female fly needs to drink an animal's blood, and so female greenheads which have laid eggs fly inland to look for prey in the area bordering the marsh; they can stay on land looking for animals to bite for up to four weeks.[3] Their bites itch, like those of mosquitoes, but are more painful, since greenheads feed by cutting a wound in the skin with scissor-like mouth parts and sucking the blood released through it. Females live for three to four weeks and may lay about 100 to 200 eggs per blood meal.[4] The eggs are laid on the grass in a salt marsh; the larvae live in the intertidal mud of the salt marsh for one or two years, preying on other invertebrates, before pupating in early spring.[3] The adult flies emerge in late spring and are most common from late June to August.[3] [5] [6]
Greenheads are large enough that their population cannot be controlled with insecticide without damaging the ecosystem.[3] Affected coastal communities install black box traps in marsh areas to reduce and control T. nigrovittatus populations.[7] [8]