Horseflies are much maligned creatures as they not only bite people, but unlike many other blood feeding animals like mosquitoes, they do not utilise any form of anaesthetic and use the painful method of using their scissor like mandibles simply chewing through the skin. As in many blood feeding organisms, it is only the female that feeds on blood, as they need it to produce eggs and the with the males feed on pollen and nectar from flowers.
Horsefly larvae can be found in damp soil and in water, and are either aquatic or amphibious. The eggs are reported to be laid in clumps on vegetation or stones, close or above the water.
When the eggs hatch the larvae drop into the water from the plants they were laid on. They are segmented bodied maggots with a head that can be retracted into the thorax, have a long cylindrical body with points at either end and are white, green or brown in colour.
They live in the mud at the edge of the water of puddle, ponds and lakes and sometimes in damp soil. At the pointed tip of the abdomen is breathing tube so they can get air from the surface.
They are carnivorous and eat other insect larvae and invertebrates, including each other. The larger species have been recorded feeding on amphibian tadpoles and even on froglets, using a pair of hooks on the mouthparts to catch prey. Many species overwinter as larvae.
Once fully grown the larvae crawls out of the water or wet soil and move to drier area of soil before burrowing into it and pupating into an adult. Adults are usually on the wing in the summer months, with some emerging in May and a few species still about in until October, with individual living about 3 to 4 weeks and can produce up to 6 batches of eggs in that time.