The order is one of the four largest groups of living organisms. There are more known flies than vertebrates. These insects are a major component of virtually all non-marine ecosystems. The economic importance of the group is immense. One need only consider the ability of flies to transmit diseases.
Flies also destroy our food, especially grains and fruits.
On the positive side of the ledger, outside their obviously essential roles in maintaining our ecosystem, flies are of little direct benefit to man. Also see the Tree of Life for information on the classification of flies. Short vignettes of various groups of flies are presented below. Each covers a family of flies, providing an image of a typical species, the range of that species and the family as whole, with a summary of what is known about the group. Information about flies at this site is arranged into 3 levels, which correspond to the family, genus and species categories.