356 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



This may look to the carper or to one who loves to chaff his ento- 

 mologist friends as a possible case of cause and effect — the more 

 entomologists, the more insects and insect damage ! But to the 

 knowing mind it is perfectly obvious that, just at the time when the 

 crisis of overpopulation of the earth is approaching, just at the time 

 when the total human food supply must rapidly be increased, the 

 multiplication of injurious insects is helped in a way by the very 

 methods man has adopted in his civilized lifel 



Instance after instance in illustration of this fact will occur to 

 you. Let us look at the cotton boll weevil. Here is a species that 

 gradually di^veloped its close adaptations to cotton in Central 

 America where the cotton tree grows wild. It was a nearly unlmown 

 creature of slight economic importance. Brought by accident across 

 the Rio Grande at Brownsville, and then more or less by accident 

 to Alice, it found itself in a boll weevil heaven — a whole State 

 growing its favorite food, and growing it in just the waj^ to make 

 life a delight, in just the way to promote to the utmost limit its 

 extraordinary powers of multiplication, and so its enormous pro- 

 gressive spread until now the whole vast Cotton Belt is occupied. 

 Incidentally it may be said that all this might have been prevented 

 had the advice of entomologists been followed in the beginning, and 

 that at a later date the spread might gi'eatly have been retarded 

 and the damage very greatly lessened had the Southern cotton 

 planters generally heeded the advice of the experts. 



This will answer as an illustration in regard to agriculture. 

 With regard to human health the same conditions hold. For ex- 

 ample, it may be shown that the advance of civilization in a new 

 country at first reduces malaria, by the drainage of swamp areas 

 and the reclaiming of moist " bad lands " for agriculture, only to 

 be followed, as the country becomes densely settled, by the reap- 

 pearance of malaria, since man has made new and even better 

 breeding places for the malarial mosquitoes than were the old 

 swamps: the making of milldams, of stone quarries, the stopping 

 of extremely small streams of running water b}' railway embank- 

 ments, the digging of borrow pits, the accumulation of old tin cans 

 and disused vessels of one sort or another about towns, even the 

 footprints of cattle in soil that is not too dry, especially during a 

 rainy season, and in coimtless other ways, such as water troughs for 

 cattle, small ornamental ponds for aquatic plants, the water recep- 

 tacles for grindstones, poorly-protected cesspools, imperfectlj''- 

 covered water tanks, the catch basins of sewer systems, the badly- 

 cared-for roof troughs of houses and barns, even the perfected and 

 up-to-date water-closets in houses temporarily vacated, and so on 

 and so on. 



