Cave insect

Accordingly, it is not surprising that a number of insects permanently inhabit caves, especially at the deepest levels, and are markedly specialised for niches in some of the extreme conditions.

[1] Caves also appear to have become the last refugium for many ancient types of insects, which are no longer found free in the open in surrounding regions.

Once adapted to troglobitic existence, cave insects become specialised and dependent on the cavernicolous conditions; when suddenly exposed to the outside world, they are likely to succumb rapidly.

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.

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.

In individual caves, the most conspicuous and perhaps most ubiquitous peculiarity of insects, as with other troglobites, is the reduction of body pigmentation.

This contrasts with most nocturnal or crepuscular species, in many of which there is a strong tendency to adapt to low light levels by responding to selection for large, highly sensitive eyes.

A form of adaptation common to many cave insects as well as some external predatory species, is elongation of appendages, especially the antennae, palps and forelegs that assist in precise location of prey before striking.

One exception is Troglocladius hajdi (family Chironomidae), which has strongly reduced eyes consisting of only 0–4 ommatidia, yet have well-developed wings and is able to fly in total darkness.

[5] The cave insects found in the Atlas Mountains include blind Trechus jurijurae, Aphaenops iblis, Nebria nudicollis with very long antennae and legs, the staphylinids Paraleptusa cavatica and Apterophaenops longiceps, and the curculionid Troglorrhynchus mairei.

The exclusively cave-dwelling silphid Adelops hirtus occurs in Kentucky caves and has very minute, unpigmented, atrophied eyes.