Invertebrate Cave Fauna 
143 
The milliped genus Trichopetalum has a much broader geographic 
distribution and fewer species (ca. 15) than Pseudotremia (see Shear 
1972). Troglobites are unpigmented and completely eyeless. Scoterpes is 
closely related to Trichopetalum and contains perhaps 30 troglobitic 
species (many undescribed) that inhabit caves to the south and west of 
the study area in Alabama, Georgia, Illinois, Kentucky, Missouri, and 
Tennessee (Causey 1960b; Shear 1969, 1972). Trichopetalum contains 
five troglobites and three troglophiles. Four of the troglobites occur in 
the Appalachians of Virginia and West Virginia, and one is known from 
northern Alabama (Causey 1960a, Shear 1972). The troglophiles occur 
in Alabama, Kentucky, Maryland, and Oklahoma (see Causey 1967, 
1969; Shear 1972), and all species possess eyes and pigment. 
The three species of Trichopetalum in the study area are apparently 
very closely related genetically, as suggested by the possibility of 
hybridization between some of the populations (see Causey 1963 and 
elsewhere this paper). This possibility, combined with the contiguous 
distribution and closely similar morphologies of the species, suggests a 
relatively recent common ancestor, possibly involving a moderately 
widespread humicolous epigean form that invaded caves over parts of 
western Virginia and eastern West Virginia. A fourth species, T. krekeleri 
(Causey), from caves in Randolph and Tucker counties, W.Va., is 
distinct, but it was probably derived from the same ancestor. 
A majority of the North American troglobitic collembolans are in 
the Entomobryinae genera Pseudosinella and Sinella. Three troglobites 
(viz., P. hirsuta, P. orba, and S. hoffmani ) and a number of 
troglophiles/ trogloxenes occur in the study area. In two recent papers 
on the zoogeography of eastern North American cave collembolans, 
Christiansen (1981, 1982) assigned caves in the Appalachian Valley and 
Interior Low Plateaus region to a category he called “heartland caves.” 
Two other categories in the eastern United States were designated 
“glaciated area caves” and “non-glaciated non-heartland caves.” As 
might be expected, the most highly specialized troglobitic collembolans 
(based on degree of troglomorphy) generally occur in heartland caves. 
In an earlier paper, Christiansen (1961) recognized two types of 
characteristics in cave species: cave-dependent and cave-independent 
characters. Using cave-dependent characters as a basis to measure 
evolutionary changes leading to an increase in troglomorphy, he devised 
a seven-step evolutionary scale for the cave Entomobryinae, with step 7 
representing the highest level of adaptation. On this scale, Pseudosinella 
hirsuta was considered to be in step 5; P. orba and Sinella hoffmani 
were in step 6. 
Troglobitic collembolans in the study area have relatively extensive 
ranges, and none is restricted to caves in a single exposure of limestone. 
Troglobites, however, have much more compact ranges than troglophiles. 
