216 THE POPULAR SCIENCE MONTHLY 



disease; and the studies made on insects, by physicians, have been as 

 important as those made on the afflicted patient. 



The identification of a species of Glossina or tsetse fly as an agent 

 in the spread and transmission of the " sleeping sickness " is one of the 

 more recent accomplishments in this direction, and opens a way for 

 dealing with this plague that has practically depopulated great areas 

 in Africa. 



This seems like a series of heavy indictments against a lot of 

 insignificant creatures whom, heretofore, we have deemed ourselves 

 justified in ignoring. But the case has been understated rather than 

 otherwise, and it is time that we recognized insects as among the most 

 dangerous enemies to man from the sanitary standpoint. 



Let me put it in a somewhat 

 different way: could we at a blow 

 eliminate all the members of the 

 single order Diptera — including the 

 fleas — we should at the same time 

 absolutely eliminate malaria, yellow 

 fever, dengue, jungle and several 

 other kinds of tropical fevers, the 

 bubonic plague, sleeping sickness, 

 a b filariasis, several forms of eye dis- 



fig. 7. Types of Maiiophaga or biting e certain ulcerating sores in 



lice. / ° 



tropical countries, and we should 



reduce to a minimum enteric fevers of all kinds, lessen the death rate 



from tuberculosis and pulmonary troubles, and probably modify or 



lessen leprosy and kindred diseases. 



But this is not all our plaint; for besides attacking man directly 

 in his bodily health and comfort, they attack his domestic and other 

 animals and lessen their value if they do not absolutely destroy them. 



Every one of our domestic animals and all our feathered friends 

 of the barnyard are infested by lice — biting and sucking and some of 

 them harbor several species. All of them are well adapted in form to 

 the conditions under which they live; and even the hog, which is not 

 usually thought of as a hairy animal, has a species that manages to 

 move about as freely as need be among the bristles. Naturally, ani- 

 mals so infested can not do their best for their masters; they become 

 mangy in appearance, do not grow well, the fowls lessen in egg pro- 

 duction and the cows in milk. 



To the dairyman, flies — comprehensively speaking — are nuisances 

 from all points of view. In the pasture Tabanids in great variety get 

 after them; in the stable Stomoxys is always on hand. Occasionally 

 the fauna of one country contributes a pest to that of another, as was 

 the case when the so-called horn-fly was introduced about twenty years 



