A New Species of Troglobitic Rhadzne (coleoptera: Carabidae) from Texas

group numbers 14. Extensive collecting from Texas caves has resulted in the discovery of numerous new A new robust species of the subterranea group of the ground beetle pOpu~ationS oftroglobitic ~ h ~ d i ~ ~ . several of these new genus Rhadine LeConte is described. Rhadine rqyesi, new species, is known from eight caves on Fort Hood, Bell and Coryell Counties.Texas. populations appear to be undescribed species. Further L The new species is thought to be most closely related to Rhadinc be required decide On of them. persephone Barr from Travis and Williamson Counties, Texas. The However, among the new populations is a distinctive genitalia of both species are illustrated and the possible value of the new species endemic to caves on the Fort Hood Military ovipositor as a taxonomic character is discussed. The first phoretic mite ~~~~~~~~i~~ in ~ ~ 1 1 and coryell counties. B~~~~~~ this recorded from a troglobitic Rhadine has been identified as Echinome~istus wheeler; (Wasmann) (Mesostigmata: Paramegistidae). material is part of an active series of studies it is desirable to describe this new species at this time. Although a few studies were conducted in Fort Hood INTRODUCTION caves in 1963 and 1964 by David McKenzie and James The subterranea group of the genus Rhadine as Reddell, troglobitic Rhadine were not known there until revised by Barr (1974) included 11 species, all 1992 when Marcelino Reyes discovered the first troglobitic, from caves in Texas. Barr (1982) added two specimen in Tippit Cave. An intensive program of additional troglobitic species, both from caves in studies on Fort Hood caves from that time until the northern Mexico. With the addition of the species present has resulted in the collection of specimens of described herein, the total species in the subterranea Rhadine from nine caves on Fort Hood. Study of this material reveals no significant differences between the populations and all are assigned to the species described below. Barr (1974) discussed the evolution and zoogeography of Texas troglobitic Rl~adine . He concluded that the most significant barriers to dispersal were major streams and that isolation of populations occurred due to erosional mechanisms, creating isolated outcrops of limestone. The Edwards Limestone is the only cavernous geologic unit on Fort Hood. This formation crops out only on the tops of several elongate mesas and stnall hilltops. All of the caves known to contain Rhadine occur in northern Fort Hood on a single elongate outcrop. A minor gap occurs in the cavernous limestone between the eastern (Tippit Cave) and western areas (remaining caves) containing popillations of Rhadine. This gap in the limestone appears to be too recent to have allowed speciation to occur between different populations of Rhadine. Geographically, the closest known species of troglobitic Rlindine is R. nocfivaga Barr in northern Williamson County. This species is separated from Fort Hood by about 30 miles of non-cavernous deposits. Furthermore, R. noctivaga is one of a series of slender species that are presumably older troglobites, whereas R. reyesi is a robust species and apparently has become isolated more recently in caves. Other species of terrestrial troglobite on Fort Hood, including spiders (Cicurina), millipede (Speodesmus), and pselaphid beetle (Batrisodes), are a l w apparently recent troglobites. The closest known species of robust troglobitic Rhadine is R. persephone from northern Travis and southern Williamson County. The new species and R, persephone differ from other subterranea group members by having a relatively wide, glabrous