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John R. Holsinger and David C. Culver 
area. The most notable example of this is mud banks, which are often 
near streams. The faunas from three such habitats are listed in Table 3. 
In Fallen Rock Cave, a layer of finely divided detritus rich in oligochaetes 
was present, and in the other two caves there were spatterings of cricket 
guano. In all three caves there was a high proportion of troglobites, 
ranging from 50% in Tazewell Saltpetre Cave to 73% in Gallohan Cave 
No. 1. In these situations, low resource density probably puts trog- 
lophiles at a disadvantage. 
Most cave streams have an alternating riffle-pool structure (shallows 
and deeps) that is characteristic of stony-bottomed streams in general. 
Most stream-dwelling cavernicoles prefer riffles for several reasons. 
First, water in riffles is well oxygenated. Second, riffles serve as traps 
for leaf litter, thus increasing availability of food resources. Species 
characteristic of riffles are the isopods Caecidotea and Lirceus, the 
amphipod Crangonyx antennatus, and the snails Fontigens. There is a 
finer division of the riffle habitat. In general, small individuals tend to 
be under small rocks, which are deep in the riffle. In a study of two 
caves in southwestern Virginia, Estes (1978) found that the small 
Crangonyx antennatus was under small rocks and gravels, but the larger 
Lirceus usdagalun and Caecidotea recurvata tended to be under large 
rocks and gravels. 
A few species are concentrated in steam pools. Flatworms seem to 
be more common in pools, where they glide along the surface of the 
water, than in riffles; but no quantitative data exist on this point. Larval 
Gyrinophilus prophyriticus are concentrated in pools, where it is 
relatively easy for them to detect prey movements (Culver 1975). 
Drip pools are the habitat of most species of Stygobromus, although 
occasionally some (especially Stygobromus mackini) are found in 
streams (Holsinger 1978). Crangonyx antennatus also occurs in pools 
(Dickson 1977a), where it frequently constructs shallow burrows, 
apparently to avoid desiccation during droughts (Holsinger and Dickson 
1977). Burrowing behavior may be widespread in Stygobromus as well, 
but this point has not been investigated. 
Life Histories 
Relatively little work has been done on life histories of cavernicoles 
in the study area. Nonetheless, because of the importance of the subject, 
a brief overview of the problem will be presented. A more comprehensive 
treatment is given by Culver (1982). In general three sorts of comparisons 
have been made. First, cavernicoles have been compared with epigean 
species (Ginet 1960, Rouch 1968). While comparisons have not always 
been made with phyletically similar species, these comparisons usually 
show striking differences between cave and epigean species. Second, 
cavernicoles of different ages in caves have been compared. Age in caves 
