On the other hand, our knowledge of the earlier states of Coleoptera is yet very imperfect as compared with the Lepidoptera. Coleopterous larvae are, with few exceptions (notably Coccinellidae and some Chrysomelidae), much more difficult to find and rear, and their distinguishing characters are more difficult to study. The few comprehensive works on Coleopterous larvae that have been published are based on rather scant material and none of them deal with the North American fauna. [Illustration: FIG. 63.--A Ground-beetle (_Calosoma calidum_). _a_, larva; _b_, adult.] Coleoptera occur in all climates and in all localities. Species are known from the highest northern latitudes ever reached by man, and in the tropics they occur in an embarrassing richness of forms. They are found in the most arid desert lands, in the depths of our subterranean caves, and on our highest mountains up to the line of eternal snow. The open ocean and the open water of our Great Lakes are the only regions free from them. As a rule, the number of species gradually increases from the Arctic regions toward the tropics, but it would be difficult to decide, speaking of North America, whether or not the fauna of the Middle States is poorer in the number of species than that of the Southern States; or whether the beetles of the Atlantic slope outnumber those of the Pacific States or those of the Central region. On the Pacific slope the influence of the seasons on insect life is greater than on the Atlantic slope. While in the latter region a number of species may be found the whole year round, there is, in the more arid regions of the West, an abundance of insect life during and shortly after the rainy season, with great scarcity during the dry season, except, perhaps, on the high mountains. Few persons have had a more extended experience in collecting Coleoptera than Mr. E. A. Schwarz, one of my assistants, and the following account has been prepared by him at my request and is given _in extenso_.