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John R. Holsinger and David C. Culver 
ECOLOGY 
Sources of Food 
Aside from darkness, the most striking feature of most caves is the 
scarcity of food. Except for a few chemosynthetic autotrophic bacteria 
that use iron and sulfur as an electron donor, primary producers are 
absent. Thus, in a general sense, cave communities are decomposer 
communities. Allochthonous food is brought in by both biological and 
physical agents in different amounts, continuously or in pulses, and in 
different spatial configurations. These differences affect the kind of 
species present, so that it is useful to review them. 
In the terrestrial biotope, there are at least five major sources of 
food: (1) bat guano, (2) cave cricket eggs and guano, (3) microorganisms, 
(4) mammalian feces and dead animals, and (5) plant detritus left by 
flooding. A few caves harbor large bat colonies with large guano 
concentrations beneath the roosting sites. In this case food is abundant, 
and the fauna feeding on guano is quite different from the rest of the 
cave fauna (Harris 1970). Caves with large bat populations are rare in 
Virginia and east Tennessee and have not been studied with respect to 
their invertebrate communities. Small piles of bat guano rarely seem to 
have any macroscopic fauna. Perhaps this is because no species are 
present that are physiologically equipped to digest bat guano. 
A major source of food input comes from the cave crickets in the 
genus Euhadenoecus. These crickets regularly leave the cave at night 
and feed “opportunistically and omnivorously as a scavenger” (Hubbell 
and Norton 1978), eating the vast majority of their food outside the 
cave. The females oviposit inside the cave, usually in sandy substrates. 
In parts of the Edwards Plateau of Texas and the Interior Low Plateaus 
of Kentucky, cave-cricket eggs are the major dietary item for some 
species of beetles. This fascinating interaction has been extensively 
studied (Culver 1982) because the cricket-beetle interaction comes close 
to being a naturally isolated predator-prey pair. This facilitates study of 
morphological, behavioral, and demographic characteristics because 
selective pressures are relatively simple and clear-cut. We have found no 
evidence that cricket eggs form a major part of the diet of any beetles in 
Virginia and east-Tennessee caves. We suspect that this interaction is 
absent because sandy substrates are rare in Appalachian Valley caves 
and Euhadenoecus species oviposit in substrates difficult for beetles to 
excavate. Cricket guano, on the other hand, is an important food 
source. Some of the most diverse terrestrial communities occur in areas 
where cricket guano is spattered on walls and floors. We suspect that in 
many caves it is a major source of food, either directly, or indirectly by 
serving as a substrate for microflora. 
Microorganisms occur on a variety of substrates, including wood, 
dung, and plant detritus. At least part of the diet of many terrestrial 
