Horse flies are a common nuisance, especially during warmer months. These robust insects are more than just a bother; their bites can be painful and persistent. Belonging to the insect family Tabanidae, and more specifically the genus Tabanus, horse flies range in size from that of a common housefly to as large as a bumblebee. They are sometimes referred to as “greenheaded monsters” due to their striking metallic or iridescent eyes, which meet on the top of the head in males but are separate in females. You might also hear them called gad flies, breeze flies, or ear flies, nicknames that hint at their annoying habits and biting mouthparts. One prevalent species, Tabanus lineola, is easily recognizable by its bright-green eyes and is often simply called a green head. Deer flies, from the genus Chrysops, are similar but typically smaller than Tabanus and have distinctive dark patterns on their wings.
Adult horse flies are known for their speed and strong flight, often found buzzing around streams, marshes, and wooded environments. While they are a pest to humans and animals alike, they also pose a health risk as potential carriers of diseases such as anthrax, tularemia, and trypanosomiasis in animals. The life cycle of a horse fly begins with females laying clusters of flat, black eggs on vegetation, typically grasses. They spend the winter as larvae, pupate in the spring, and emerge as adults usually by late June.
It’s the female horse flies that are notorious for their blood-sucking habits, making them significant pests to both humans and animals. In large numbers, they can consume considerable amounts of blood from their hosts – sometimes three ounces or more in a single day. In areas where flies of the Haematopota genus are overly abundant, agricultural work during daylight hours can become unbearable, forcing activities to be shifted to nighttime when these flies are less active. In contrast to their blood-thirsty female counterparts, male horse flies have a gentler diet, feeding on nectar, honeydew, and plant sap.
Controlling horse fly populations can be challenging. Methods include eliminating breeding grounds by draining or oiling marshy areas. However, insecticide sprays are often ineffective. For livestock and pets, physical barriers like blankets or fly nets offer some protection against horse fly attacks.
