Notes on some North American Odonata, with descrip- 33 HORN, G. H., M. D. The species of Heterocerus of Boreal America 1 A Revision of the Sphæridiini inhabiting Boreal America 279 Some Notes on Aræoschizus. 339 HULST, GEORGE D. The Phycitidæ of North America. 93 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. |