Entomology and Other Sciences 287 



RELATION OF INSECTS TO HUMAN LIFE AND TO THE 



SCIENCES.^ 



J. J. Davis, Purdue University. 



It was recently remarked that a scientist is one who tells us some- 

 thing which everyone knows, in a language which no one understands, 

 this originally being given by a distinguished ecologist as the definition 

 of ecology. It is not my purpose to talk on technical investigations but 

 rather to discuss a general problem that we may better understand the 

 science in which I am interested, the relation it bears to the science 

 which each of you are interested in, and how we may better correlate and 

 utilize our knowledge. I feel certain that if I were more familiar with 

 the general subject which each of you are specializing in I could cor- 

 relate my own work to better advantage. We are already doing this 

 in the purely agricultural sciences, as I hope to point out later. 



It rarely occurs to one that the innumerable little crawling and 

 flying creatures known under such names as bugs, beetles, flies and 

 worms, belong to the dominant order of living creatures. The dominance 

 of insects — "is another way of saying that the number of fixed variations 

 of structure, form, color, and the like, to be found in insects is greater 

 than that presented by all other land animals. By reason of this extra- 

 ordinary power of variation, and hence of adaptation — of fitness to 

 various conditions and situations — insects are very widely distributed, 

 and are found in a greater variety of places and surroundings than any 

 other class of land animals on the earth. They are able to maintain 

 themselves, in other words, in a greater number of ways and to avail 

 themselves of a larger variety of the resources of the earth than any 

 other animals" (Forbes). Insects "are small, extremely tenacious of 

 life and endowed with such great powers for reproduction and mul- 

 tiplication that the abundance of any particular species responds very 

 rapidly to changes in food supply, or other variable factors in their 

 surroundings" (Brues). We all know that now and then some section 

 of the country is overrun with grasshoppers, that chinch bugs ruin 

 the corn in some regions, that the army worm may appear suddenly 

 and practically denude certain regions of vegetation. These are only 

 conspicuous manifestations of a struggle that goes on everywhere and 

 continually in which insects are always threatening to devastate the 

 earth and we fail to see or recognize the innumerable insects which are 

 ready to show their voracious habits and become destructive should 

 conditions, either weather, methods of farming and the like, or unfavor- 

 able conditions for their natural enemies, favor them. We fail to recognize 

 the battles between harmful insects and their natural enemies which 

 are going on everywhere about us; we fail to realize the fact that in- 

 sects are not only destructive to crops and animals, and are annoying 

 pests, but that they carry innumerable diseases of plants, of animals 

 and of humans, and that because of this latter fact render some parts 



^ Presented at the 1922 meeting. Contribution from the Department of Entomology, 

 Purdue University. 



"Proc. Ind. Acad. Sei., vol. 33, 1923 (1924)." 



