The mosquito is only too familiar to every one from {41}its ceaseless attacks; it occurs almost everywhere, but is most abundant in marshy situations. The larva (Fig. 1a) inhabits all stagnant waters, where it may be found very abundantly throughout the summer, and when disturbed it plunges about with great agility. Its food consists of the numerous animalculæ swarming in all still waters during the greater portion of the year. These are captured by means of two curious anterior appendages, which are fringed with long hair, and pulled through the water like a fisherman's net; they are then withdrawn into the mouth and the contents devoured, the hungry insect again extending them for a fresh supply. These larvæ are generally seen suspended from the surface of the water by the curious air-tube which takes its rise from the penultimate segment of the abdomen, which is of considerable length. Its apex is armed with a row of stiff bristles, which effectually prevent the water from entering the spiracle there situated, so that the insect is enabled to respire when hanging from the surface, independently of any muscular action. It is also worthy of note that the intestine discharges itself into this tube, an arrangement which does not exist among the British species. After several moultings the transformation to the pupa state takes place. At this stage the insect (Fig. 1b) becomes much thickened anteriorly, this being the region of the head and thorax of the future gnat; all the limbs are easily detected on a close examination, as with lepidopterous pupæ. The upper portion is provided with two short appendages, fulfilling the same function as the air-tube of the larva, and which constantly support the pupa at the surface of the water. The terminal fins enable it to dash through the water with great rapidity when pursued by enemies; at other times it remains perfectly motionless, suspended from the surface of the water. It should be mentioned that none of these aquatic pupæ take any nourishment, neither have they any limbs properly {42}so called. Their locomotion, although in some cases unquestionably rapid, is entirely effected by violent motions of the abdomen. I have been careful to point out these peculiarities as these animals have been regarded by many authors as _active_ pupæ on a level with those of the Orthoptera and Hemiptera. This opinion, however, is manifestly erroneous; the pupæ of the nemocerous Diptera are on precisely the same footing as those of the Lepidoptera, and it would be almost as reasonable to call one of these _active_, because it wriggles out of its cocoon in the earth before the emergence of the moth. The perfect mosquito emerges from a rent in the thoracic shield of the pupa, drawing each pair of legs out separately, and placing them in front of it on the water; the wings and abdomen are then extracted and in a few moments it flies away.