590 REPORT UNITED STATES GEOLOGICAL SURVEY. 



The facts here presented may often seem disconnected and desultory, 

 but few except experts in natural history are perhaps aware how diffi- 

 cult a task it is to follow out the transformations of any particular in- 

 sect, and study thoroughly its habits in its different stages of growth. 

 Unlike fishes, birds, and quadrupeds, which have similar habits at all 

 stages of growth, an insect, with its three separate stages of larva, pupa, 

 and adult, leads, as it were, three lives, with different surroundings, and 

 in each of these stages may be regarded as a different animal. Then it 

 is often extremely difficult to ascertain of what beetle or moth or bee 

 such or such a grub or caterpillar is the young. Our entomologists are 

 not numerous enough, and often, from their time being taken up with the 

 pursuit of their profession, usually not that of science, are unable to be 

 long enough in the field to observe for themselves the habits of insects. 

 Unfortunately, also, so backward is the science of entomology in this 

 country, that its students are at present fully engrossed with, the labor 

 of classifying and describing the adult insects. When it is to be borne 

 in mind that there are within the limits of the United States, probably 

 at a low estimate, 10,000 species of Hymenoptera (bees, wasps, ichneu- 

 mon-flies, saw-flies, etc.), nearly as many butterflies and moths, about 

 10,000 species of two- winged flies {Diptera), as many beetles {Coleoptera) 

 and bugs (Hemiptera), and several thousand species of grasshoppers, 

 etc. [Ortlioptera)^ and neuropterous insects, such as dragon-flies, cad- 

 dis-flies, etc., etc., the whole amounting to upward of 50,000 species of 

 insects, not to speak of the spiders, mites, and ticks, centipedes and 

 millipedes, it is evident that in the mere preliminary work of identif^^- 

 ing and properly describing these myriad forms — an intellectual work 

 requiring quite as much good sense, discretion, and knowledge as is 

 shown in the i)ursuit of medicine, the law, or teaching — it is evident 

 that all this work, which is simply i^reliminary in its nature, is a vast 

 one, and that the combined exertions of many minds over several gen- 

 erations will not exhaust the subject. As it is, there are in this country 

 only about thirty entomologists who publish anything relating to in- 

 sects. Necessary as it is, this work of classification is by no means the 

 highest and most useful branch of natural science. He who studies 

 carefully the habits and structure of one insect, and, if it is injurious to 

 agriculture, lays before the farmer or gardener a true story of its life, is 

 a true benefactor to agriculture, and at the same time benefits science 

 more than he who describes hundreds of new species. 



We have little idea how many kinds of insects are preying upon our 

 field and garden crops, our shade, ornamental, and forest trees. There 

 are, probably, within the limits of pur country 5,000 difterent kinds, 

 which are either at present engaged in the work of devastation, or are 

 destined to be, with the growth of civibzation, which means in this in- 

 stance the destruction of the natural food of these insects and the sub- 

 stitution of a similar diet, our choicest grains and fruits, in its stead. 



In the densely-popnlated countries of Europe the losses occasioned 

 by injurious insects are most severely felt, though from many causes, such 

 as the greater abundance of their insect-parasites and the far greater 

 care taken by the people to exterminate their insect-enemies, they have 

 not proved so destructive as in our own land. MM. Pasteur and Qua- 

 trefages, whose names are illustrious as original investigators, were com- 

 missioned by the French government to study the causes of the silk- 

 worm disease, j?;e6ri!we, and, as the result of their studies, silk-eulture,an 

 interest involviog millions of dollars, will probably again be restored to 

 France and Italy. Itshould be remembered thatthisremarkable result is 

 due, primarily, to the most abstruse researches upon a microscopic plant 



