AbstractsBiology & Animal Science

The genus Coenonycha contains 30 described species of small to medium sized scarabs. They are found in the arid and semi-arid regions of western United States and northern Baja California. The adults feed at night on several genera of xerophylous plants. An examination of the male genitalia of the 19 long-winged species indicates that the internal sac possesses characters which are stable within a species and are, therefore, taxonomically useful. These structures are a dorsal, toothed, knob-like sclerite and from one to four spinose fields on the enlarged portion of the sac. Variation in these structures within a species occurs in the number of teeth on the knob and spines in the fields. Sixteen new species of Coenonycha were discovered in the course of this study. They are indicated by letter in the text and phenetic tree and will be described elsewhere. The male genitalic structures of the 19 long-winged species are described in detail and illustrated. A key to these species, using primarily the basal knob and spinose fields is included. In addition, a key (modified from Cazier and Mc Clay, 1943) to all the described species of Coenonycha, using characters such as color, pilosity, clypeal reflection and pronatal punctation is provided. A key to the North American genera of Macrodacylini using the parameres, basal piece, basal apodeme, genital segment, and internal sac shows the diversity of genitalic structures in the tribe. Coenonycha, Dichelonyx, and Gymnopyge are presently placed with Macrodactylus and Isonychus in the Macrodactylini. Based on genitalic, larval, spiracular, and adult external morphological structures, Coenonycha, Dichelonyx, and Gymnopyge should be separated from the Macrodactylini and placed in the tribe Dichelonychini.