AMERICAN MUSEUM OF NATURAL HISTORY C.-E. A. WINSLOW AND FRANK E. LUTZ GUIDE LEAFLET No. 48
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INSECTS AND DISEASE A Statement of the More Important Facts with Special Reference to Everyday Experience BY C.-E. A. WINSLOW AND FRANK E. LUTZ American Museum of Natural History GUIDE LEAFLET No. 48 NEW YORK, JUNE, 1918 PRINTED AT THE MUSEUM
‘“*T deal with certain little Invertebrata; animals which work in darkness and in stealth, little anima!s which in times of Peace we politely ignore, yet little animals which in times of War may make or unmake an army corps. As that wise old Greek, Aristotle, wrote—and he knew quite a lot about them—‘One should not be childishly contemptuous of the study of the most insignificant animal. For there is something marvellous in all natural 2) A. £. Shipley, “Minor Horrors of War.” objects.’ ’
INSECTS AND DISEASE By C.-E. A. Winslow and F. E. Lutz THE IMPORTANCE OF INSECTS The life of man is affected, for good or ill, at a thousand points by the activities of the humbler members of the living world of which he forms a part. The lower animals and plants supply us with our food and clothing and with materials for providing shelter against the elements. On the other hand, certain species are our relentless foes, waging constant war against our property and even our lives. In the case of the insects, for example, as we review the multitudes of these creatures within our limited horizon, we not only admire the wondrous beauty of this species or the amazing instincts of that; we are awestruck at the financial havoc wrought by one and appreciate with gratitude the way in which another helps to restore the balance of Nature and protect us from starvation. Even among the microbic forms of life, in the world of the “‘infinitely little,’’ we find, on the one hand, the bacteria of the soil fixing the nitrogen of the air and making it available for our growing crops — on the other, the bacilli of tuberculosis and of a score of other deadly diseases, threatening the health and life of hundreds of thousands.
One of the most interesting and important chapters in the story of the interrelationships between mankind and the lower forms of life is that which deals with the triple relation between the microbe, the insect and the human being in the spread of certain communicable diseases. The types of insects and their relatives concerned are, on the whole, more disgusting than beautiful; their habits are not attractive, nor are their instincts extraordinary; but they have profoundly influenced the history of the human race. You and | may lose our lives by reason of their activities; we certainly can aid in combating them. It, therefore, behooves us to become well acquainted with our foes.
AMERICAN MOSEOUM GOIDE LEAPLE AS.
CHARACTERISTICS OF INSECTS First of all, a word should be said as to the characteristics of these creatures and their place in Nature. Those animals which have no internal skeleton but do have, at some period of their lives, jointed legs are called Arthropods. Familiar examples are lobsters, spiders, centipedes, and insects. We are now chiefly concerned with certain insects but we must also consider mites and ticks, creatures which are more closely related to the spiders. An insect has its body divided into three regions: head, thorax, and abdomen. Its jointed legs are borne by the thorax, the segments of the body which are just back of, but separated from, the head; there are never more than three pairs of such legs in an adult insect. Spiders, mites, and ticks have, typically, four pairs of jointed legs, and the head is merged with that part of the body which bears the legs.
The great majority of insects are winged, when adult, and most winged insects have two pairs of wings, but the members of the large Order Diptera, to which mosquitoes and flies belong, have never more than one pair. Nearly all of the strictly parasitic insects are wingless, even when adult. We will take up first those disease-bearing insects which have, when adult, one pair of wings, next certain wingless insects, and finally the mites and ticks. Two sorts of Diptera or two-winged insects are of interest in the present connection: (1) ordinary “‘flies’’ with three-jointed antenne; and (2) mosquitoes, gnats, etc., which have eight or more freely moving joints in each antenna. The Muscide and the Tabanide (p. 13) are of the first sort.
The Muscide, a group which includes our commonest diseasebearing insect, the filth fly, are characterized as follows: The squame (see Fig. 1) of Diptera are scale-like structures placed back of the roots of the wings and above the knobbed “‘balancers’’; and the Muscide agree with the related Diptera in having these squame large. The auxiliary vein in the wing (see Fig. 1) is distinct in its whole course, and the first longitudinal vein is never very short. The thorax has a complete transverse suture. The eyes of the male are usually much nearer together than those of the female; sometimes, in fact, so close that they touch each other. 4