) in a cave in
Thailand eating
guano The climate in deep caves typically is without distinction of day and night, But insects have a sleeping pattern and not many are affected even by the passage of the seasons. Violent winds and storms are unknown, though there may be steady air currents under some circumstances.
Humidity is roughly stable. Communications with the outside world only occur under special conditions such as floods and exceptional droughts. Where streams pass through caves or water seeps in, they commonly are important sources of
nutrition. Trogloxenes are important to cave ecology, because they commonly feed outside and import material that serves as food when they return. Insect species such as some
butterflies,
flies, and beetles over-winter in caves, and casualties remain as food. Cavernicolous
bats, being trogloxenes, are major ecological factors in some caves where they spend their daylight hours, and some species such as
Mexican free-tailed bats provide massive deposits of
organic matter, mainly in the form of
faeces and
carcasses. Other trogloxenic animals include vertebrates such as
bears,
hyenas, other predators, reptiles,
oilbirds,
cave swiftlets and even humans, that enter for short term shelter or for hibernation. Most of them contribute organic matter rather than consuming it, and are important resources for troglobitic insects, many of which actually specialise in reliance on particular species that are long-term regular visitors. The cave environment thus is characterised by absence, restriction, or attenuation of certain factors such as light,
circadian or seasonal
stimuli, living space, freedom of movement, or abrupt contrasts in temperature and humidity. Other items may depend on local conditions; for example, most caves provide little available food and some provide little water, whereas some provide
perennial water or quantities of dung so great as to support ecological stratification, with organisms preying on other organisms that live in turn on different stages of the original product. The ultimate sources of nearly all food in caves are outside the cave. Running water and air currents carry in carcasses and other organic
detritus.
Fungi and bacteria that develop on this material provide food for many cave dwellers. Bat
guano represents another source.
Lepidoptera that enter caves for sleeping are preyed upon by troglobitic
Orthoptera, largely
Tettigoniidae and
Gryllidae. The cavernicolous Collembola feed on
colloidal matter in the water or dust borne on the
surface tension. The insects and similarly sized invertebrates are food for spiders and
Myriapoda. Most such activities go on in darkness, except close to the outside, or where certain microbes or insects such as
Arachnocampa provide
bioluminescence, even if only to attract prey. == Evolutionary characteristics ==