The resting position of Anopheles is pecu liar in that the head, body and tail present a straight line, at an angle with the resting sur face, while in the Culex and Stegomyia the body is bent as you observe in Fig. 8.
The eggs of C. pungens (Fig. 9), the gutter mosquito, are cone-shaped and float on end, being glued together in large masses to main tain this position in the water. The number deposited by a single mosquito varies from 50 to 400, and they hatch in from one to three days, varying according to temperature and en vironment. When a sufficient time has elapsed to complete the hatching process, the larva (Fig. 10) or wiggle tail issues from the shell and begins to feed on the vegetable and animal matter contained in the water.
In its growth the larva sheds its skin several times before the pupal stare is reached—in from 7 to 10 days. Mosquito wigglers get along apparently without air, when the surface of the water is covered with ice, and it is possible that they get air then, in the same way that fish do. This would account for their not being de stroyed by surface freezing of the water. Ento mologists must decide whether or not the larva have gills or some organ analogous to the gills of the fish. The wigglers of some mosquitoes may be frozen in ice and hibernate until liber ated by warmer weather.
The pupal stage in mosquito life corresponds to that of the chrysalis in the transition of a caterpillar into a butterfly (Fig. 11). The pupa does not teed. In about two days it becomes an imago, which is the technical name for the com pleted insect whose life begins with the ovum or egg.
The shell of the pupa breaks at its highest point and the completed mosquito issues, being supported by the floating shell until its wings spread for flight (Fig. 12).
The kind of mosquito that issues from the shell of the pupa depends of course on the kind of egg which has been deposited and hatched in the water.
The life cycle of Culex, the gutter mosquito, is from 10 to 15 days. Do not mistake the life cycle for the length of life; mosquitoes may live as adult insects for many months, and some fe males must hibernate through the winter to furnish eggs for the next summer's supply.
Eggs of Anopheles (Fig. 13), the swamp mosquito, arc boat-shaped and float singly on the surface of stagnant pools. They are depos ited in numbers between 40 and 100. The bot tom of the floating egg is marked somewhat like mosquito netting, the pattern being raised. The top of the egg is smooth, black in color and partly covered by a transparent membrane which stands out from the surface of the top and sides, permitting intervening spaces of air, which float the egg like a lifeboat. The egg hatches in from three to four days.
The larva of Anopheles (Fig. 14) may be readily distinguished by its position at the sur face of the water, as well as by its general ap pearance, differing from that of either Cukx or Stegomyia. You will observe that the neck of the Anopheles larva is very slender, and that the head is turned upon the body. This is be cause the Anopheles larva finds its food on the surface and gathers it by the constant motion of little broom-like processes projecting from the sides of the mouth, and furnished for this purpose.
The breathing tube, you will observe, pro jects from the back or upper surface of the larva, near the tail end. To get its mouth to the surface while maintaining its position for breathing, requires that the head should be turned half round on the body, an impossible position to any but the thin-necked Anopheles larva.
The larva becomes a pupa (Fig. 15) in about 12 days. In about five more days the pupa is a full-grown mosquito.
Eggs of Slegomyia (Fig. 16), the yellow fever mosquito, float singly upon the surface of the water and are deposited in numbers varying from 5 to 75. They hatch in from 10 hours to 3 days, according to climatic and other conditions. The shell is marked like mosquito netting, the white pattern being raised and somewhat sim ilar to that of the Anopheles egg, and on the sides are air-chambers which float it.
The larva (Fig. 17) is very similar in ap pearance to that of the Culex, and its position in the water is also similar to Culex and unlike Anopheles.