cave fauna, then, are just a part of a sometimes

inaccessible interstitial fauna that exists over a

much wider subterranean area. If this is the case,

then the fauna of a particular cave may not

be as isolated as it initially seems, since it may be

connected with neighboring caves by cracks and

tiny corridors that allow insect populations to pass

from cave to cave without having to go outside.

In northern parts of the northern hemisphere,

such as Britain, caves are common in chalk and

limestone districts and are well studied, but no

associated troglophile cave fauna are known. This

is thought to be because they were scoured and

sterilized by the cold and ice of recent glaciers,

and the cave insects have not had any opportunity

to recolonize. It is interesting to speculate what

might have inhabited these caves before the

glaciations of the last Ice Age. Farther south in

Europe, for example in Hungary, the Balkans,

Italy, or Spain, and at equivalent latitudes in Asia

and North America, a rich troglophile fauna of

detritivores and small predators adapted to the

environment are found, and many unusual new

species are being discovered.

The low level of available nutrients means

that true cave fauna usually has low populations

which are widely spread within the cave and

surrounding soil. Biospeleologists use traps set over

many months—baited with strong-smelling foods

and drinks such as cheese, beer, and wine—in

order to lure individuals of this fauna, but even

after a year or more a trap may yield only a small

number of specimens.