Cave Insect - Evolutionary Characteristics

Evolutionary Characteristics

In individual caves not all the numerous cavernicol insects, the most conspicuous and perhaps also universally met with peculiarity is the reduction in body pigmentation. This is particularly marked in Coleoptera. The reduction or total loss body pigmentation are without doubt correlated with the absence of sunlight. This is demonstrated by the fact that all these unpigmented cave beetles readily develop the characteristic pigment when they are exposed to sunlight. A second peculiarity is the more or less pronounced reduction of eyes in all caverniculous species. Nearly all cave insects are characterized by an abnormal elongation of appendages, especially the antennae, as compensation for loss of eyes. There is also increase and elongation of sensory setae, as for example, in the beetle Scotoplanetes arenstorffianus from Herzegovina. In contrast, none of the free-living related carabids have such sensory setae on the elytra. True cave insects are generally all characterized by wing reduction. Among the cave beetles the hind wings are reduced or even lost.

The general appearance and attitude of body of cave insects often differ conspicuously from those of free-living relatives. This is particularly observed in Silphidae, through nearly every other cave insect also exhibits this peculiarity. All these are evidence not of selection, as commonly assumed, but of direct functional adaptation and correlation to the immediate environment.