Horsefly - There are over 30 species of horsefly. They are found worldwide except the polar regions and absent in Greenland, Iceland, and Hawaii. Although active at night they prefer to fly in bright sunlight. Horseflies or Clegs as sometimes referred to, are a flying insect found most in rural farmland areas where they feed on large mammals. Only the female horsefly bites to obtain blood for producing ova. The male has weaker jaws that prevent it from biting. Because they prefer semi-aquatic habitats and damp conditions they are more abundant after a rain shower and become more of a pest. Although bites to humans are painful, itchy and troublesome they are not usually harmful. They do however spread disease in horses which can be fatal if the horse develops diseases such as swamp fever. They can reduce milk output from cattle and spread disease among them. This fly was photographed in Co Leitrim Ireland.