1657. DIPTERA. Dipterous insects are distinguished by having only two wings; but they are lobed, or slightly divided at their hinder base, so as to represent the additional pair of wings common to most insects. The tarsi are of five joints; the mouth is lengthened into a proboscis armed with lancets; and there is no anal sting. Dipterous insects, in general, have neither size nor beauty to recommend them; yet, from their numbers, they hold a very important station, and are designed to carry on many essential operations in nature. Their larvï¾µ are either aquatic or terrestrial; the former principally living upon smaller insects, and the latter drawing sustenance from decayed animal or vegetable matter, and thus hastening its removal. In this order we find many species highly injurious to vegetation, and others that are offensive and troublesome both to man and beast.