Cave Insect - The Cave Environment

The Cave Environment

The general climate in a cave is remarkably unvaried and without distinction of day and night. The differences between summer and winter conditions are also greatly moderated. Violent winds and storms are unknown, though there are steady air currents. The humidity condition changes but very little. Communications with the outside world are on the whole minimum. The river flowing or water seeping in from the outside insures regular quantities of nutritive material. The bats that feed outside but sleep in the cave likewise provide massive deposits of organic matter by way of fecal droppings and dead bodies. In addition to bats, a variety of other animals penetrate caves for sleeping or for over-wintering: butterflies, flies and other insects, bears, hyenas, and even humans. The cave environment is thus recognized largely by negative characteristics, viz. absence of light, lack of rhythm of day and night and of seasons, scarcity of available food, limitation of living space, restricted freedom of movements, absence of contrast, absence of marked changes in temperature and humidity.

The ultimate source of food for all cave animals lies naturally outside the cave. Rivers carry in cadavers and other organic debris. Fungi which develop on this detritus provide food for many cave dwellers. Bat guano represents another source. Lepidoptera that enter caves for sleeping are preyed upon by cave grasshoppers. The caverniculous Collembola feed on colloidal matter on the water. The Collembola and cave beetles are devoured by spiders and myriapods. All these activities go on in total darkness.