There is now a world-wide crusade against mosquitoes, extending from the wilds of Africa through the noted malarial districts of Italy to America. In America a National Mosquito Extermination Society has been formed. This extensive crusade is due to the practical demonstration that some kinds of mosquitoes may transmit malaria, yellow fever and probably other diseases of human beings. All mosquitoes must have water in which to develop, and the warfare against them consists largely in destroying their watery breeding grounds. This is being done on a large scale, either by draining or by filling in marshes, pools, and similar places which often swarm with the "wigglers." Large areas of such mosquito-breeding waste lands in New Jersey and on Long Island are thus being reclaimed and the mosquito nuisance largely abated. Aquaria, rain barrels, tanks, small ponds and similar places can be kept free from the "wigglers" by introducing small fish, as gold fish or silver fish, sunfish, "killies," roaches or minnows. An interesting and instructive object lesson could be given by putting a few minnows from a near-by brook into the school aquarium or into a specially prepared glass dish well stocked with the "wigglers." One can easily prevent mosquitoes from breeding in rain barrels or tanks by covering them with mosquito netting. Another practicable and successful method is to pour or sprinkle kerosene oil every two or three weeks in a thin film over the surface of cesspools, rain barrels, tanks, ponds or any other body of sluggish water where the "wigglers" are found. This oil film kills the "wigglers" (both larvæ and pupæ) by preventing them from getting to the surface to breathe, and it also prevents the mother mosquito from laying her eggs on the water. There are patent preparations or oils which penetrate all through the water, killing the "wigglers" but spoiling the water for general use, so that such oils are usually applied only to infested cesspools, sewer basins, or manure pits. By a little concerted effort of local officials, individuals, or by the school children in applying whichever of the above methods is most practicable, much interesting and valuable work could be accomplished and the pestiferous mosquito largely eliminated in many localities. LEAFLET XXI. THE WAYS OF THE ANT.[27] BY ANNA BOTSFORD COMSTOCK. [27] Home Nature-Study Course, Vol. V, No. 1. October, 1903. [Illustration] For many years ants have been recognized as among the most interesting of the little animals that people our fields. However, not until recently have we begun to understand, even in a small measure, their economic importance and the part they play in maintaining the balance in insect life. Therefore, we shall give a few studies of ants and their ways, and as a knowledge of their habits is necessary to begin with, we will take up the ant-nest first. AN ANT-NEST.