Invertebrate Cave Fauna 
97 
Most cavernicoles in streams feed directly on detritus and its 
associated microorganisms. The epigean amphipod Gammarus pseudo- 
limnaeus Bousfield is a facultative shredder (Cummins and Klug 1979), 
preferring CPOM, but also using FPOM and DOM. Cave-stream 
amphipods are probably similar in this regard. No direct information on 
isopods is available, but Estes (1978) suggests that Lirceus usdagalun 
tends to eat CPOM whereas Caecidotea recurvata tends to eat DOM. 
On the basis of their size, crayfish are probably shredders, and snails 
and lumbriculid worms probably ingest DOM. 
The diet of cave flatworms is more problematical than that of 
crustaceans. Mitchell (1974) has demonstrated that Texas cave flat- 
worms ( Sphalloplana sp.) eat injured and moribund amphipods and 
crickets. Holsinger (1966), on the other hand, suggested that flatworms 
eat tubificid worms. The greatest concentrations of flatworms that we 
have observed in cave streams have been in stream pools with no 
amphipods or isopods. We suspect that flatworms feed on small 
oligochaetes and perhaps on microorganisms. 
The primary stream predator is larval Gyrinophilus porphyriticus. 
These salamander larvae are voracious feeders on amphipods and 
isopods (Culver 1973b, 1985) and appear to be exclusively predaceous. 
They are generally limited to caves with high densities of amphipods 
and isopods. 
The amphipods and isopods occurring in drip pools and in deep 
phreatic lakes ingest the organically rich mud. Guts of animals from 
these habitats are often filled with mud, as can be seen in the photograph 
of the cirolanid isopod Antrolana lira (Fig. 13A). Dickson (1975) shows 
that abundance of Crangonyx antennatus in pools is correlated with 
abundance of microfungi. A tentative food web for pool habitats in 
Banners Corner Cave is shown in Figure 33, based on Holsinger’s (1966) 
study. 
Habitats 
Because of the scarcity and patchiness of resources, terrestrial 
cavernicoles are often concentrated on discrete patches of dung, wood, 
and plant detritus. Examples of the fauna found in these habitats are 
listed in Table 2. The most interesting pattern that emerges from Table 
2 is that the frequency of troglobites is lowest on dung (20%), slightly 
higher on patches of plant detritus (28%), and much higher on wood 
(76%). The difference between wood and the other habitats is highly 
significant (G = 9.44 P > 0.99). As Poulson (1978) pointed out, 
resources with high caloric value and low residence time, such as dung, 
should have a high frequency of vagile troglophiles with relatively high 
reproductive rates, compared with long-lasting resources having low 
caloric value, such as wood. 
Cavernicoles also are found in habitats that are less discrete, where 
resources are more or less homogeneously distributed over a larger 
