MUSCA, in natural history, the fly, a genus of insects of the order Diptera: mouth with a soft exserted fleshy probos cis, and two equal lips; sucker furnished with briitles; feelers two, very short ; antenna generally short. This is a very numerous genus ; not fewer than a thou sand species have been enumerated. They are divided into sections; vit. A. with short feelers ; and B. without feel ers. These sections are again separated into others. The larva in the different tribes of flies differ far more in habit thins the complete insects, some being terres trial, and others aquatic. Those of the common kinds are emphatically distin guished by the title of maggots, and spring from eggs deposited on various putrid substances. Several of the aquatic kinds are of singularly curious formation, and exhibit wonderful examples of the provision ordered by nature for the pre servation of even the meanest of animals. The general form of the pupa is that of an oval, differently modified, according to the species, and formed by the external skin of the larva. Some speciescast their skin before their change into the pupa state. One of the most remarkable spe. cies is M. chameleon, which is a large black fly, with a broad flattish abdomen, having the sides of each segment yellow, forming so many abrupt semi-bands across that part. It proceeds from an aquatic larva, of very considerable size, measur ing two inches and a half in length, which is common in stagnant waters during the summer months, and passes into its chry salis state without casting its skin, which dries over it, so as to preserve the former appearance of the animal in a more con tracted state. M. terms is a remarkable insect, about the size of a drone, of a brown colour, with transparent wings. It
proceeds from a larva of a very singular appearance, being a long-tailed brown maggot, of rather a slow motion, measur ing about three quarters of an inch in length. This maggot is seen in muddy stagnant waters, drains, and other places of the dirtiest description : and, notwith standing its unpleasant appearance, ex hibits many particulars well worthy of ad miration : the feet are wonderfully cal culated for enabling the animal to ascend walls, or other perpendicular places, in order to seek some proper situation, in which it may undergo its change into chrysalis, being very broad, and beset on their under surface with numerous small hooked claws, giving it the power of clinging with security during its ascent. The larva commonly changes to a pupa about the end of August, the skin con tracting and drying round the body, and the tail continuing in a shrivelled state. After remaining in this state about &fort night, it gives birth to the complete in sect. It is common in England in the month of September, and is often mista ken for a drone. Among the bristly flies is the M. carnaria, or common blow-fly, which deposits its eggs on animal flesh, either fresh or putrid. The larva, or mag. gots, hatch in the space of a few hours, and when full grown, which happens in eight or ten days, they are of a yellowish colour, with a slight tinge of pale red. When the animal changes to a pupa, the skin dries round it, and the whole assumes a completely oval form, and a reddish co lour. In ten days after the fly emerges.