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The Diptera or true flies are an amazing order of insects which can be readily recognised in their adult forms because those which have wings, and most of them do, have only two, all other flying insects have four wings; in the true flies the hind wings have become modified into a pair of balancing organs called halteres.

Flies are one of the major success's of the insect world, and the 120 000+ species are divided into three sub-orders, the Nematocera, (larva with complete head and horizontally biting mandibles, pupa obtect, generally free, antennae of adults usually many segmented, pleural suture of mesothorax generally straight); the Brachycera, (larva with incomplete head and vertically biting mandibles, pupa obtect, generally free,antennae of adult generally three segmented, pleural suture of mesothorax twice bent); and the Cyclorrhapha, (larva with vestigial head, pupa exarate, usually in a puparium, antennae of adult with three segments, pleural suture twice bent, head with frontal lunule and a ptilinum), and these in turn are divided into about 100 families.

Flies can be found in most places in the world, and the common house fly Musca domestica has followed mankind to every corner of the earth. There are 6 500+ species of fly living in Britain alone.

Flies have a holometabolous life cycle, this means that the egg hatches into a small grub like creature which doesn't look anything like a fly at all, you have probably all seen maggots and mosquito larvae. The larvae eats and grows and occasionally sheds its skin until it is big enough to make an adult fly, then it pupates, in the more advanced forms inside its old larval skin (unlike most insects and the less advanced flies which shed their larval skin before they pupate) and changes into and adult fly.

Because there are so many species of flies with so many different life styles it is difficult to generalise however larval flies live nearly everywhere in the soil, the ponds and streams, the sea in plants and animals, and eat nearly everything from dung and decaying plant material through living plants to animals including us and even other flies.

Flies are great opportunists and as adults they also eat a great variety of foods, though some don't eat at all. The mouth parts of adult flies are all designed either for sucking and sponging, or piercing and sucking, no adult fly can chew its food, biting flies actually should be called stabbing flies. Flies have been of incredible importance to mankind all over the world, and it is possible to say that on many occasions it has been a fly which has changed the cause of history. This is because many of the primary diseases of man are transmitted by flies. (This means the disease is actually caused by a bacterial, viral or protozoan agent which spends part of its life in a fly and gets into the person when a fly pieces that persons skin) two examples are Malaria (transmitted by mosquitos which is believed to have killed more human beings than any other known disease and is still a major cause of illness in many countries, and Yellow Fever. It is well known that the predications of the tetse fly on both people and livestock has been the main obstacle to European colonisation of North Africa.

Spiders and Flies

Though everyone thinks of spiders feeding primarily on flies, and it is true that spiders eat an awful lot of flies, the spiders don't always get it all their own way. A Dance Fly Microphorus crassipes (Empididae) steals much of its food from the spiders own web. Robber Flies (Asillidae) have been observed catching and eating spiders which were sitting on a blade of grass. A whole family of flies the Cyrtidae (about 250 species) are all internal parasite of spiders during their larval life. The eggs are laid on the ground and the first instar larva wait on damp vegetation for a passing spider. They leap up and attach themselves to the spiders body where they slowly eat their way through its cuticle before eating the spider from the inside out.

Flightless flies.

Not all flies can fly some have given up their wings and in some cases their halteres as well. this has occurred in a number of families, including the Fungus Gnats (Mycetophilidae) i.e. Epidapus venaticus, Midges (Chironomidae) i.e. females of the genus Pontomyia, Crane-Flies (Tipulidae) i.e. the snow-fly Chionea sp which lives above the snow line in Europe in temperatures as low as -10 C, Coffin-flies (Phoridae), some species of Louse-Flies (Hippoboscidae) i.e. the Sheep Ked Melophagus ovinus, and the Bee-louse Braula caeca (Chamaemyiidae); both the Bee-louse and the Sheep-ked can be found in this country.

Though some flies are very common and can be found all over the world some are very rare i.e. Mormotomyia hirsuta a largish fly which lives in a crack about a meter wide in the rocky outcrop at the top of Ukazzi Hill in Kenya. The larva feed on the dung of the bats which also live in this rocky crevice, and it is believed the adults feed on the sweat and other body secretions of the bats. This is the only place in the world where this fly has ever been found

Because of the large number of species of flies in the world, around 100 different families it would be impossible to tell you about them all, so the rest of this article will introduce you to a number of flies and then tell you some interesting facts about them.

Blue Magpies Nest: Blue Magpies Nest is a collection of essays and poetry suitable for all the family to read, quarranteed to amuse and stimulate you.