The six endangered karst invertebrates protected by the Balcones Canyonlands Conservation Plan are all troglobites. A troglobite is an animal that is specially adapted to living underground, spending their entire lives in caves. Adaptations to this environment can include small eyes or complete lack of eyes, long appendages, and reduced pigmentation. Most species are believed to feed on tiny insects called microarthropods as well as decomposed organic matter. However, relatively little is known about the biology of these endangered karst species.

The Tooth Cave Ground Beetle is a reddish-brown beetle approximately 7 to 8 mm in length. It is the most active of the endangered invertebrates, searching the cave floor for prey and digging holes into silt to feed on cave cricket eggs.

The Tooth Cave Pseudoscorpion is a large, eyeless pseudoscorpion that is golden brown in color. The pseudoscorpion, about 4 mm in length, does not have a tail. It is usually found under rocks and uses its pinchers to prey upon microarthropods.

The Tooth Cave Spider is a small, whitish spider with long, thin legs. With a length of 1.6 mm, it is the smallest of the listed invertebrates. It feeds on microarthropods, hanging from a small web.

The Kretschmarr Cave Mold Beetle is a small shiny, reddish-brown beetle with short wings and long legs. It is found in total darkness under rocks and buried in silt.

The Bone Cave Harvestman is a blind, pale orange harvestman. Harvestmen, sometimes referred to as daddy longlegs, are spider-like arachnids with small bodies and long thin legs. It is especially sensitive to low humidities and in the hottest parts of summer can only be found in the coolest, dampest parts of the cave.

The Bee Creek Cave Harvestman is an orange color, with long legs and well-developed eyes. It preys on tiny, hopping insects called collembolans. It is usually found under rocks in darkness or dim light.