9.6. Cavernicolous insects

Caves often are perceived as extensions of the subterranean environment, resembling deep soil habitats in the lack of light and the uniform temperature, but differing in the scarcity of food. Food sources in shallow caves include roots of terrestrial plants, but in deeper caves there is no plant material other than that originating from any stream-derived debris. In many caves nutrient supplies come from fungi and the feces (guano) of bats and certain cave-dwelling birds, such as swiftlets in the Orient.

Cavernicolous (cave-dwelling) insects include those that seek refuge from adverse external environmental conditions — such as moths and adult flies, including mosquitoes, that hibernate to avoid winter cold, or aestivate to avoid summer heat and desiccation. Troglobiont or troglobite insects are restricted to caves, and often are phylogenetically related to soil-dwelling ones. The troglobite assemblage may be dominated by Collembola (especially the family Entomobryidae), and other important groups include the Diplura (especially the family Campodeidae), orthopteroids (including cave crickets, Rhaphidophoridae), and beetles (chiefly carabids, but including fungivorous silphids).

In Hawai’i, past and present volcanic activity produces a spectacular range of “lava tubes” of different isolation in space and time from other volcanic caves. Here, studies of the wide range of troglobitic insects and spiders living in lava tubes have helped us to gain an understanding of the possible rapidity of morphological divergence rates under these unusual conditions. Even caves formed by very recent lava flows such as on Kilauea have endemic or incipient species of Caconemobius cave crickets.

Dermaptera and Blattodea may be abundant in tropical caves, where they are active in guano deposits. In south-east Asian caves a troglobite earwig is ectoparasitic on roosting bats. Associated with caverni-colous vertebrates there are many more conventional ectoparasites, such as hippoboscid, nycteribid, and streblid flies, fleas, and lice.

Chapter 9