[Illustration: _Fig. 153. The active pupa._] The larval stage lasts about ten days in hot summer weather, but longer when the days are cool. Then comes a change in form into the pupa (Fig. 153). The creature is still active and aquatic, though no food is taken. It does not stay long away from the surface while in this stage. Finally, after two or more days as a pupa, the full-grown mosquito emerges and takes wing, leaving its pupa case floating on the top of the water like a forlorn little derelict. ENEMIES OF THE MOSQUITO. Besides man, the mosquito has many natural enemies. In the water especially they fall easy victims to the thousand-and-one insect ogres. The nymphs of dragon-flies are especially fond of wigglers, and there has been much said and written about raising dragon-flies as a safeguard against mosquitoes. Most of the predaceous insects which live in still water feed on young mosquitoes, while the adults often fall prey to their more swiftly flying insect neighbors. HOW TO STUDY THE MOSQUITO. Over and around the tumbler place a piece of close-woven mosquito netting to confine the adult insects. A glass tumbler two-thirds full of rain-water, a little cluster of eggs, or a half dozen wigglers, a keen observer, and you have a nature-study opportunity not to be surpassed in the finest laboratory. If you have already seen a part of the life history, do not be satisfied until you have completed your chain of observations. Get the eggs; watch the hatching, the molting, the transformations. See every stage. Learn something new every time you look at the wiggler or the mature mosquito. It is not at all necessary that you let these insects escape into the school-room and cause trouble. Those who wish more minute description, with many illustrations of mosquitoes of different kinds, should obtain from the Division of Publications, Department of Agriculture, the published results of Dr. L. O. Howard's studies of mosquitoes. In this pamphlet, from which the drawings in this lesson are copied, the subject of the transfer of disease germs by mosquitoes is very thoroughly discussed, with pictures which distinguish between the common mosquito and those which transfer malaria and other diseases. Those scientists who had to do with the naming of the many species of mosquitoes had certainly a sense of humor. One would think they named the creatures according to the mildness or malignity of their bite. A few of the names are as follows: Culex excitans Culex pungens Culex irritans Culex stimulans Culex perturbans Culex excrucians THE CRUSADE AGAINST MOSQUITOES. BY M. V. SLINGERLAND.