The Cavernicolous Beetles of the Subgenus Rhadine, Genus Agonum (Coleoptera: Carabidae)

Abstract

The carabid beetles of the subgenus Rhadine Leconte are an interesting series of slender, depressed, wingless Agonum which are distinguished by their elongate appendages, strongly oblique humeri, and the absence of normal pigmentation; all known species are uniformly testaceous, rufotestaceous, or dark ferrugineous. In the majority of species the third antennal joint is longer than the fourth, although this character is often allometric, the third joint being proportionately much longer in larger species and individuals than in smaller ones. In many species, but not all, the elytral apices are produced and dehiscent to a greater or lesser degree. A lateral series of setiferous elytral punctures, three or four in the margin below the humerus and a variable number (range about 10 to 15) on the 8th interstria or in the 8th stria, is usually well-developed. The scutellar and apical elytral punctures are setiferous. The first three tarsomeres typically bear lateral grooves. The undersides of the legs are, in most Rhadine, sharply flattened from base to apex, the edges rectangular and parallel. Species referable to Rhadine range from southern Canada to the northcentral plateau region of Mexico and east to Maryland and the coastal plain of Alabama, but the known species are most numerous in the southwestern United States, especially Arizona, New Mexico, and Texas. They are most common under rotting logs and rocks in moist situations (especially at high altitudes), in the burrows of mammals, and in caves. The cavernicolous habit has been reported for A. (Rhadine) longicolle (Benedict), known only from Carlsbad Caverns, New Mexico; for A. (Rhadine) ozarkense (Sanderson and Miller), known from a single Arkansas cave; for A. (Rhadine) caudatum (Leconte), known from numerous localities in the eastern United States; and for one troglophile and three troglobitic species in Texas (Barr and Lawrence 1960). Three new troglophile and three new troglobitic species are described in the present paper.