Invertebrate Cave Fauna 
141 
exposure of cavernous limestone in the Powell Valley of Lee County 
(see Holsinger 1967b). In the adjacent Clinch Valley, A. paynei, a 
probable sister species, inhabits caves that are developed in several 
separate exposures of limestone. 
Miktoniscus racovitzai (5. lat.), the only eyeless, troglobitic member 
of its genus, is closely allied morphologically with epigean congeners in 
the eastern United States (see Vandel 1950). It is probably a relatively 
recent derivative of a widespread, preadapted troglophile ancestor. In 
comparison, Amerigoniscus comprises 10 eyeless, unpigmented species, 
of which nine are troglobites and seven are recorded from single 
localities. The widespread, highly disjunct distribution of the species in 
this genus (viz., three from northwestern Georgia, one from south- 
central Oklahoma, two from Oregon, one from middle Tennessee, one 
from northwestern Texas, and two from the study area; see Vandel 
1965a and 1977, Schultz 1982), combined with the fact that all are of 
troglobitic facies, suggests that members of this genus are old, isolated, 
subterranean relicts of a formerly widespread surface fauna. With the 
exception of A. rothi (Vandel) from an endogean habitat (under rocks 
and moss in a dense forest; see Vandel 1953) in Curry County, Oregon, 
no other epigean congener is known. 
Recent studies by Zacharda (1980, 1985) indicate that a majority of 
the cavernicolous rhagidiid mites in the North American and European 
faunas are troglophiles and that only a few species have well-developed 
troglomorphisms and are restricted to caves. Because the family 
Rhagidiidae is predominantly edaphic and some of the edaphobites 
occur in caves, it is reasonable to assume that the troglobites are 
relatively recent derivatives of soil-dwelling forms. Of the two species 
considered troglobitic in the study area, one ( Foveacheles paralleloseta ) 
is known only from a single cave, whereas the other ( Rhagidia viria ) has 
a much broader distribution and is recorded from caves in several 
drainage basins. 
None of the eight spiders considered troglobitic in the study area 
has a range that is limited to a single, continuous exposure of limestone. 
As already mentioned, the ranges of the troglobitic linyphiid spiders are 
among the most extensive of all troglobites in North America. Several 
explanations for these broad ranges have been suggested (Holsinger 
1963a, Barr 1967a, Holsinger et al. 1976, and elsewhere this paper), but 
until the genetics of the species are studied, nothing definitive can be 
said. However, the presence of eyes (although variable) and some 
pigment in many populations, combined with the wide ranges, strongly 
indicates that these species are recently evolved troglobites. 
Compared with linyphiids, nesticid spiders have much smaller 
ranges. Troglobitic nesticids show varying levels of eye and pigment 
reduction and appendage attenuation. Gertsch (1984) has pointed out 
