A Horseflies Bite Is Extremely Painful

Horseflies are considered pests for the bites that many inflict, they are among the world’s largest true flies. They are known to be extremely noisy during flight. They are also important pollinators of flowers.
The bite from a large specimen is painful. Most short tongued species of horse flies use their knife-like mandibles to rip and/or slice flesh apart. Flies with longer tongues bite more like a mosquito, their stylet-like mouthparts piercing the host’s skin like needles.
The horsefly’s modus operandi is less secretive than that of its mosquito counterparts, although it still aims to escape before their victim becomes conscious of the pain signals. Moreover, the pain of a horsefly bite may mean that the victim is more concerned with assessing the wound, and not swatting the interloper. In any case defense is difficult, considering the agile nature of the fly. The bites may become itchy, sometimes causing a large swelling afterward if not treated quickly.
Horse fly season is in the summer and early fall, they like the warmer weather. They also prefer wet areas,  lakes and beaches. Horse flies are attracted to dark objects and use their complex, compound eyes to locate prey. Horse flies appear to be attracted to certain odors, as well as to carbon dioxide.