Entomologist: Horseflies are thriving this summer, unlike mosquitoes
Due to low rainfall, people have enjoyed a break from mosquitoes this summer, but horseflies are doing well, according to entomologist Urmas Tartes. He explains that horsefly larvae develop in permanent water bodies, and their bites are much more painful.
This summer's dry weather has reduced mosquito numbers, but horseflies, whose bites are considerably more painful, are thriving, says entomologist Urmas Tartes.
Speaking on Vikerraadio, Tartes noted that blood-sucking insects often appear where people least expect them. For example, horseflies may seek prey over asphalt roads. He recounted that while driving to the Lõunakeskus shopping center, a beautifully patterned horsefly approached him in the parking lot in broad daylight, seeking a blood meal.
According to the scientist, people's perception of insect abundance largely depends on their habits and expectations. Due to the prolonged dry spell, there are hardly any mosquitoes in the forests, and people quickly became accustomed to an early summer without biting insects. This is why horsefly attacks seem particularly surprising this year.
The difference in mosquito and horsefly numbers is directly linked to their larval development conditions. While all insects developing in water need moisture, mosquitoes depend on puddles formed after snowmelt and heavy rains. The scarce rainfall at the start of summer caused these breeding sites to dry up. Horsefly larvae, however, live in thick layers of mud in lakes and ponds, and their life cycle is not interrupted even in adverse weather. They develop in permanent water bodies that do not fully dry out, and since the larvae can move, they travel wherever water is available as levels change.
Air temperature also influences insect activity. Both mosquitoes and horseflies prefer more humid weather, but cool conditions make them sluggish. At around ten degrees Celsius, they almost stop flying, and as it warms up, mosquitoes are the first to appear. When temperatures reach 20 degrees, the sun's heat activates larger insects, including horseflies.
A horsefly active in hot weather bites using significantly coarser jaws than a mosquito, making its bite far more painful. A mosquito pierces the skin with a fine proboscis, leaving a tiny opening that barely damages tissue and does not cause bleeding. A horsefly, in contrast, tears the tissue apart to access blood.
The insects that cause the most concern are usually the huge horseflies that approach with a loud buzzing. According to Tartes, the largest of these, known as ox or bull horseflies, are about the size of a child's thumb. As their name suggests, they prefer to feed on the blood of large animals and, in his experience, attack humans relatively rarely.
Only females feed on blood because they need it to develop eggs, meaning only half of the population are bloodsuckers. Males stay away from mammals and primarily consume plant sap and nectar.
As a protective measure against horseflies, it is recommended to wear light-colored clothing and avoid dark colors, which are especially attractive to these heat-loving insects.
