Page:Popular Science Monthly Volume 63.djvu/460

456 hundred eggs upon the surface of some quiet water, and in a day or two these eggs develop into the larval or second stage (see Fig. 2).

It will be noticed that Culex hangs with its head down, and from its tail upward to the surface of the water extends a small tube. Through this tube it breathes. Anopheles rests just beneath and parallel to the surface of the water, and its breathing tube is much shorter than that of Culex. These resting positions are quite different, and each is characteristic of its kind. Except when disturbed. Anopheles is generally to be found at the surface, breathing and feeding in this position. Culex, on the other hand, comes to the surface only occasionally to breathe. It stays below the water for the greater part of the time, and is often found feeding from the bottom.

At the end of a few days the larvæ change into the pupal or third stage (see Fig. 3). To the left is seen the larval skin out of which this pupa has just come. The difference between Culex and Anopheles in this, the final stage of 'wiggler' existence, is very slight. Both now

live at the surface of the water, and they breathe through two funnel shaped tubes situated one on each side of the thorax, or 'head.' Unless disturbed, they remain motionless in this position at the surface until the time comes when, as adult mosquitoes, they leave the water (see Fig. 4). This is the critical period of a mosquito's life; for, should