LIST OF PAPERS. BASSETT, H. F. New species of North American Cynipida CALVERT, PHILIP P. Notes on some North American Odonata, with descrip- PAGE . 59 33 The species of Heterocerus of Boreal America A Revision of the Sphæridiini inhabiting Boreal America 279 Some Notes on Aræoschizus . 339 Descriptions of some new species of Agrotis Auct. 83318 TRANSACTIONS OF THE AMERICAN ENTOMOLOGICAL SOCIETY. VOLUME XVII. The species of HETEROCERUS of Boreal America. BY GEORGE H. HORN, M. D. With most collectors Heterocerus does not seem to have been held in much regard. The species have been looked upon as almost inseparable, and the small amount of literature devoted to them has been practically inaccessible to nearly all. To myself they had been equally unattractive until the large material which had accumulated in a quarter of a century required to be dealt with and properly arranged, a task of no small difficulty in a mass of several hundreds from all parts of our country in every style of cabinet preparation. In a work of this character, after the specimens have been uniformly mounted and prepared for study, the first essential step is the separation of the sexes. This is not a matter of much difficulty, although the males are far less numerous than the females. In the males the head is larger and more prominent, the mandibles more slender and projecting, the labrum longer, and in one group prolonged at middle in a process of varying length according to the species. The clypeus is also retuse to a varying degree, and is especially well marked in the species with a prolonged labrum. The thorax is at least as broad as the elytra, sometimes slightly broader, and not gradually narrowed to the front as in the female. TRANS. AM. ENT. SOC. XVII. (1) JANUARY, 1890. In one species, pusillus, the males have at the base of the mandibles a lobe prolonged over the labrum. Pl. 1, fig. 16. The separation of the species, although much less difficult than had been supposed, is not a thoroughly easy task, and the large series before me, while rendering the attempt far more difficult than it would have been with a few score of specimens, has made it possible to determine the limits of variation with greater certainty. The attempts at a monograph by Kiesenwetter were merely descriptions of species based for the most part on small series, separated without reference to structural characters. Color and sculpture afforded him the means of satisfactory separation, but with large series these are shown to have but little value. In 1866, Schioedte attempted a division of the genus on characters drawn principally from the antennæ; Augyles, one of the subdivisions having but ten joints. The recognition has been shown by deGozis to be extremely difficult and uncertain, and therefore of doubtful value. In 1872, Mulsant and Rey proposed a means of subdivision based on characters of far easier observation and giving apparently more satisfactory results. It was observed by them that in certain species the elevated curved line on the first ventral segment extended from the front angle by a broad curve toward the middle of the posterior edge of the segment and there terminated, while in others the line continued the curve forward toward the inner edge of the coxa. In the former case the abdominal plates are called open (plaques abdominales ouvertes) and in the latter entire (plaques abdominales entières). For the species with entire plates the name Augyles was erroneously adopted, which deGozis has proposed to change to Littorimus (Rev. Ent. 1885, p. 120). In our fauna but one species is known to belong here, auromicans. Recently Dr. Sharp has observed a character of considerable importance in its application to the grouping of the species. In rather more than half our species there will be observed on the metasternum an elevated line which begins at the middle of the posterior border of the middle coxa, extending obliquely backward joining the suture between the metasternum and its episternum. That this has anything to do with stridulation as suggested by Dr. Sharp seems to me extremely doubtful from its character as well as Biol. Cent. Am. vol. i, pt. 2, p. 116. |