[General Directions.]—Owing to their hard outer skeleton, Coleoptera can be collected, handled, and preserved with greater safety and with less trouble than most other orders of insects. From this fact, and from their very great diversity in form, Coleoptera have, next to the Lepidoptera, always been favorites. As a consequence, there are now more species described in this than in any other order, and in the large museums they are much better represented than other insects. This rich material has been studied by numerous and competent specialists, and the classification of Coleoptera is at present more advanced and more accessible than that of the other orders. This fact gives stimulus to neophytes, and though the literature of our North American fauna is much scattered and we are still in want of comprehensive works (with the exception of the general “Classification” by Drs. Le Conte and Horn), yet, except in a few hitherto neglected families and smaller groups, the species are fairly well worked up.
On the other hand, our knowledge of the earlier states of Coleoptera is yet very imperfect as compared with the Lepidoptera. Coleopterous larvæ are, with few exceptions (notably Coccinellidæ and some Chrysomelidæ), much more difficult to find and rear, and their distinguishing characters are more difficult to study. The few comprehensive works on Coleopterous larvæ that have been published are based on rather scant material and none of them deal with the North American fauna.
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.
[Winter Collecting.]—There are more species of Coleoptera hibernating in the imago state[3] than in any other order and winter collecting is therefore most profitable in many respects. For instance, great swampy tracts which are inaccessible in the summer season harbor an abundance of rare Coleoptera, which either can not be found in summer time or are found at that season with the greatest difficulty. At the approach of winter, however, all or most of these species will leave the swamp and seek drier ground, where they hibernate under old leaves, under bark of trees, or in rotten stumps near the edge of the swamp. Such places will, therefore, give a rich harvest to the Coleopterist late in the fall, during warm spells in midwinter, and in very early spring. If the temperature is below the freezing point, or if the ground is frozen hard, no winter collecting should be attempted, first, on account of sanitary considerations, and also because the Coleoptera then retreat more deeply into the ground and can not be found so easily as when the ground is free from frost. Other good collecting places in winter are the accumulated old leaves along the edges of forests or under the shrubbery along water courses, thick layers of moss, and the loose bark of dead or dying trees, and, finally, also under the bark of certain living trees, e. g. Pines, Sycamore, Shellbark Hickory. Digging in the ground at the base of large trees or rocks also yields good returns. The only instruments necessary for winter collecting are the sieve, the chisel, and the trowel.
[Spring Collecting.]—With the first days of spring, collecting becomes a little more varied. The methods used for winter collecting can still be continued with good success. Certain spring flowers, notably Willow blossoms, will furnish many valuable species, which are not seen again during the rest of the season.
Fig. 64.—A Lamellicorn (Pelidnota punctata).
a, larva; b, pupa; c, beetle; d, e, f, enlarged parts.