FLEAS, minute wingless insects with bodies covered by a strong armor of fine scaly plates and mouth-parts formed for sucking. They constitute the order Siphonaptera and are re lated to the Diptera. Everyone is familiar with these troublesome parasites of man and domestic animals, but few persons have studied them sufficiently to know the larval and pupal stages, or to recognize the fact that there are many species. Only recently has it been es tablished that the flea most annoying to human beings in America is not the human flea of the Old World (Pulex irritans), but the so-called dog-and-cat flea (Pulex serraticeps). Both species are of cosmopolitan distribution, but the former is fortunately extremely rare in this country, while the latter is to be found everywhere. Observations conducted by the United States Department of Agriculture have shown that the development of these insects is hastened by a moist or humid atmosphere. The egg stage is very short, the larva:, which are worm-like, spin cocoons in which the pupal stage is formed in from 7 to 14 days after hatching and the imago appears five days later, showing that in the warmest weather an entire generation may develop in little mo e than a fortnight. Fleas will develop successfully in any situation where they are not too much dis turbed, as in rugs, mats or in straw or litter on which cats or dogs have slept; and they are also carried from one place to another by rats and mice and other animals. Dr. C. F. Baker ascertained in 1895 that there were 47 valid species of fleas in the United States; and probably this number might be doubled if all of the parasite of our larger animals were known. While many persons are indifferent to the pres ence of fleas others suffer severely from their attacks. Very many alleged cases of "hives'
have been found to be produced by fleas, and epidemics of fleas in restricted areas as for ex ample, in several neighboring houses, have been traced to the body of an animal which had died near by. The fleas desert the dying body of their host, jump on the clothing of any person passing and are thus carried from house to house. One means of protection against them consists in avoiding carpets, and keeping the floors painted and covered with rugs, which should be frequently moved, swept and aired. Household pets should be kept out of the house during the summer time; in fact, it is better to exclude cats entirely, because they cannot be washed and freed from parasites so readily as dogs. Rats and mice also carry these and other parasites. The best remedy for those who suffer from fleas is to apply ammonia as strong as can be borne and as soon as possible to the bite, which in some persons is followed by an eruption as big as a dime, attended by severe itching. The free use of baking soda would serve nearly the same purpose where ammonia cannot readily be obtained. Consult Howard & Marlatt, 'Household Insects of the United States,' is sued by the Department of Agriculture; Anon., Teaching Fleas to Act (in Illus trated World, Vol. XXIV, p. 768, Feb. 1916); Anon., Huge Model of the Flea (in Scientific American, Vol. CX, p. 259, New York 1914); Bishopp, F. C., 'Fleas' (U. S. Agriculture De partment, Bulletin No. 248, Washington 1915); Dall, W. H., 'Educated Fleas' (in American Naturalist, Vol. XI, p. 7, Boston 1877); Rus sel, H., The Flea' (London, n. d.).