INSECT. 637 INSECT. thousands upon thousands of individual insect enenjies, but is affected by scores and even liun- dreds of species. A tabulation of the insect enemies of the apple already recognized in the United States shows 281 species, of clover 82 species, and of so new a crop as the sugar-beet 70 species. The insects of the vine or the orange, of wheat, and in fact of all of the prominent staples, sliow equally startling figures. It is this damage done by insects injurious to agriculture that has given rise to the compara- tively new branch of applied science known as economic entomologj", which, although origi- nating in Europe, has been encouraged to such an extent in the United .States, owing partly to the greater necessities of a new country and partly to the practical turn of mind of the American, that there are more official economic entomologists employed by the .States and by our general Government than in all of the other countries of the world together. A>ide from cultivated crops there is hardly any product of man's ingenuity 'which is not dam- aged directly or indirectly by insects — the tim- bers of dwellings, household utensils, clothes, nearly everything used as food, books, furniture, and drugs, and an infinite variety of other use- ful substances. They are very injurious to live stock and other animals: practically every species of animal which has become domesticated and is of value to roan possesses its insect para- sites and enemies. Some of them are general parasites of warm-blooded animals; others are specific to the animals or groups of animals which they affect. Horses, cattle, and sheep all have insect enemies which are not only very deleterious to their health, but frequently cause their death in numbers. The bot-fly of the horse lives in the larval condition in incredible num- liers in the stomach and intestines of the horse. The bot-fly of the ox lives, in the larval stage, under the skin of the backs of cattle, and by its perforations ruins their hides for commercial use. The bot-fly of sheep inhabits the nasal and orbital sinuses of sheep and produces insanity and death. (See BoT.) The horn-fly, the numer- ous gad-fly, including the tsetse-fly of Africa, the screw-worm fly of the Southwestern United States ( qq.v, ) , and many others, seriously hinder the efforts of the owners of live stock, IxsECTS AND DiSEASK. As annoying man him- self, insects play an important part, since there are very few regions of the habitable globe where man is not troubled by them. Bedbugs, fleas, lice, the itch-mite, the screw-worm fly. mos- quitoes (qq.v.), and many other species unite in this method of damage to the hiunan species. It is. however, as carriers of disease that insects are perhaps of the greatest importance in their rela- tions to the human species. The filaria diseases of the East (elephantiasis, chyluria, and lymph scrotum) are transferred by certain mosquitoes; the Texas fever of cattle in the United States, the red-water diseases of Africa, and other cattle fevers are transmitted by certain ticks; the tsetse-flj- of Africa carries the micro-organisms of disease; the purxilent conjunctivitis of the Eg^-p- tians and Fiji Isl.anders is communicated by the house-fly: the eye disease, known as 'pinkeye' in the Southern I'nitcd States, is transported by minute flics of the genus Ilippelates. .siatic cholera and typhoid fever are carried by the liouse-flv; and it is claimed that the bubonic plague is spread by fleas. All forms of malaria are carried about by mosquitoes of the genus -■Anopheles (see Mosquito), and yellow fever by tho.se of the genus Stcgomj'ia, (See Mosquito,) It has also recently been claimed that dengue fever is in Syria spread by a mosquito of the genus C'ule.x; that Anthrax bacilli in malignant pustules in human beings are caused by the bite of flies of the genera Tabanus and .Stomoxys; and that the famous 'surrah' disease of cattle in Oriental regions is also carried by gad-flies. Poisonous Insects. Certain in.sects may be considered under this head which poison human beings in any one of several difi'erent ways : ( 1 ) They may have a sting which is a modified ovi- positor, and which is connected with a specific poison-gland, as with the bees, wasps, stinging ants, and certain other Hymenoptera, (2) There may be a modified salivary gland which has a poisonous secretion and is connected with a piercing beak, as with certain bugs of the order Heteroptera, and as with many dipterous insects like mosquitoes and other biting flies. (3) The hairs covering the body surface may be modified into sharp bristles, which may be simple or barbed, and which, when coming in contact with the skin of human beings, produce an urticating or nettling effect. Poisonous insects of this group are confined to the caterpillars or larvae of cer- tain moths, especially of the family Limacodidse, and, to a much less marked extent, a few of the caterpillars of Bombycidae, such as Orgyia leuco- stigma, Euproctis chrjisorrhcra. as well as to a few of the Satumiidic, like the larva of the lo moth, (4) Certain beetles when crushed pro- duce a blistering effect upon the skin. These are confined to the family Meloida; or blister- beetles (q.v.). The poison of bees is formed by the mixture of the secretions of two glands, one of which is acid and the other alkaline. With the burrowing wasps the alkaline gland is absent or atrophied, an,d the poison consists only of the acid. The effect of the sting of these wasps is to stupefy the prey and not to kill it. It results that the insects .stung remain in excellent condition as food for the larrte of the wasps for a considerable length of time. (See Wasp.) The severity of the sting of the aculeate Hymenoptera and the amount of poison injected into the wound differ with different species. The sting of our large mud-wasp (q.v.) is especially severe, and as a rule the .stings of wasps have a more poisonous effect upon human beings than the stings of bees. There arc cases on record where many bee-stings on the same individual have produced death. Several instances have been well authenticated by medical men of the death of a human being from a single sting of a wasp, the sting acting as a very powerful irritant poison on the nerve- centres of the patient. As a rule such cases are confined to exceptionally ner-ous individiials. to those inheriting gouty tendencies, who are remarkably susceptible to the action of certain medicines. Persons handling bees and wasps be- come immune to their poison : the stings have little clTcct upon them. This immimity, however, disappears in the absence of continuous rein- ocilation. This f.ict is well known to bee- keepers, and entomologists who collect wasps and other stinging Hymenoptera in large numbers have called attention to the same fact. The rem-
