1896.] ESSAYS. 77 



northwest, the orange groves and vineyards of California, and the 

 great orchards and potato fields of oth(fi- States. The tracts offer 

 great quantities of desirable food, and thus stimulate tlie reproduction 

 of insects to a remarkable degree. The spread of imported species to 

 the very confines of civilization is accelerated by an ever-increasing 

 traflic on newly constructed highways and railways, and as these im- 

 ported insects escape most of their natural enemies by being brought 

 to this country, and find more favorable conditions awaiting them 

 here, their fecundity and destructiveness are increased in undue pro- 

 portion even to their increased food supply. Such are the cabbage 

 butterfly, the wheat midge, the Hessian fly, the gypsy moth, and 

 others. Native species which were harmless to agriculture under 

 natural conditions in the wilderness sometimes take advantage of the 

 introduction of a new and succulent food-plant and follow it back 

 from the frontier into the agricultural regions, spreading over the 

 whole country, and causing widespread injury to a staple crop, as did 

 the Colorado potato beetle. Man also destroys his friends, the insect- 

 eating animals. As the land becomes settled and the ravages of in- 

 sects increase, the settlers, instead of endeavoring to protect and 

 foster the useful birds that were designed to dispose of the surplus 

 insect production, pursue them until the larger useful species are nearly 

 if not quite extinct. The wild turkeys, grouse, prairie chickens, wild 

 pigeons, ducks and geese, plovers, woodpeckers, blackbirds, larks, 

 robins, and all birds which are " good for food," are slaughtered re- 

 lentlessly, even at the season when the callow young must perish from 

 starvation if deprived of parental care. The grasshopper-eating buz- 

 zards and all hawks and owls are shot at sight anywhere and every- 

 where by all classes of people. 



While all this is going on insects increase apace. The number of 

 species of insects upon the globe is vast. The number of individuals 

 is beyond all comprehension. The reproductive capacity of insects is 

 such that could a single species be allowed to increase without check 

 its progeny would soon cover the habitable earth. The following 

 statement by Dr. J. A. Lintner, the distinguished entomologist of the 

 Empire State, illustrates the maximum reproductive capacity of an 

 insect : — 



" Professor Riley in his recent studies of the hop vine aphis (Phor- 

 odon liumill ) has observed thirteen generations of the species in the 

 year. Now, if we assume the average number of young produced by 

 each female to be one hundred, and that every individual should at- 

 tain maturity and produce its full complement of young (which, how- 

 ever, never can occur in nature), we would have as the number of the 



