ORDER DIPTERA.
Including the Gnats, Midges, Crane Flies, Hawk Flies, Bee Flies, Breeze Flies, Bot Flies, and their Allies.
The Diptera, or two-winged flies, are among the most numerous orders of insects, but they have been so little studied hitherto that we have but a very imperfect knowledge of them, especially as regards the tropical species.
Fig. 120.—Midas Giganteus.
The number recorded in the British Isles is about 3,000, that of the whole world probably exceeds 30,000, and it is certain that this number will be increased immensely as time goes on.
The Diptera may be defined as insects with a sucking mouth (Haustellate), and with only two wings, which are membranous, while the hind wings are represented only by a pair of small knotted organs, called halteres. Their metamorphoses are complete.
The larvæ are footless "grubs," generally with a soft body, but sometimes leathery or even nearly horny. Many of them possess a distinctly marked head, which may contain ocelli, but in the majority the head appears as if it were simply one of the neighbouring segments.
