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Background for Teachers - Life in a Cave - Part 2

Cover-Cave Creatures

Life in a Cave - Part 2

On the Student Research Pages we introduced your children to the three categories of cave animals: trogloxenes, troglophiles, and troglobites. We've included the basic descriptions here again for you with some additional elucidation.

In addition, when animals within these categories live in water they are subcategorized. You may or may not want to get this technical with your students. If so, we’ve included the information here for you.

Trogloxenes - "Cave visitors"

MUST COME AND GO from the cave

  • These animals use caves but usually belong to surface ecosystems.
  • They'll use caves for nests, hibernation, roosts, maternity posts.
  • Examples: Bats, raccoons, skunks, snakes, bears, harvestmen

Stygoxenes – "Aquatic cave Visitors"

MUST COME AND GO from WATER of the cave

These are aquatic trogloxenes.

    • Example: aquatic isopods

Troglophiles "Cave lovers"

CAN COME AND GO from the cave

      • These animals can live completely underground, but also occur in surface ecosystems.
      • Examples: Earthworms, beetles, crickets, frogs, cave crickets, some types of harvestmen ("Daddy longlegs")

Stygophiles "Aquatic cave lovers"

CAN COME AND GO from the cave WATER

      • These are aquatic troglophiles.
      • Examples: cave snails, aquatic isopods

This blind aquatic isopod is a STYGOBITE. Because of the complete lack of light within the dark zone, it will spend its entire life with no need for vision. (© William R. Elliott)

Troglobites "Cave Dwellers"

MUST STAY in the cave

      • These animals live permanently and exclusively in caves.
      • The caves in the region of the Edwards Aquifer near San Marcos have some of the most unique cave animals in Texas. This area alone has 108 known species of troglobites!
      • Crustaceans, arachnids, and insects make up the majority of troglobites.
      • Examples: Endangered Texas blind salamanders, cave beetles, cave spiders, some types of harvestmen.

Stygobites "Aquatic cave dwellers"

Blind Cavefish

This blind cavefish is a STYGOBITE. It has adapted to the permanent blackness of the dark zone of the cave and has no need for eyes.

MUST STAY in the cave's WATER

      • These are aquatic troglobites.
      • Groundwaters in caves in the region of the Edwards Aquifer near San Marcos have 55 known species of stygobites.
      • Animal species that live only in waters underneath the ground are STYGOBITES. These are pretty rare and pretty strange animals and only about 8% of known aquatic animals live in groundwaters.
      • Examples: cavefish, cave crayfish, aquatic isopods
Daddy Longlegs

This congregation of "Daddy longlegs" was photographed by Dr. William R. Elliott, a renowned cave biologist. This photo would be a fun way to teach your students to use gridding to estimate how many arachnids there are in this picture. (© William R. Elliott)

Daddy Longlegs – Extra Cool Cave Critters!

We have a photo with a caption that introduces the topic of the harvestman to the children on the Student Research Pages, but you'll want to spend a little extra time on "Daddy longlegs" because these are some extra cool critters!

Daddy longlegs, or harvestmen, are especially interesting cave critters because you'll be apt to find harvestman species in each of the three cave zones. In other words, in a single solution cave you'll probably find harvestmen that are trogloxenes, troglophiles, and troglobites.

It's not uncommon to find harvestmen near the entrance to caves in droves! There, these long-legged arachnids often create colonies that number in the thousands. Harvestmen found in dark zones are often those that have evolved to no longer have pigment (or now have very little). In addition, in the dark zone, you won’t see them hanging out together in the huge numbers like they do on the surface or at entrance zones.

While you may think a "Daddy longlegs" is a spider since it has eight legs, a harvestman is not. One reason is that it lacks a sectioned abdomen. Instead, a harvestman’s body is one single piece. Also, instead of having 6-8 eyes like a spider, a harvestman has only two.

Two types of Texas harvestmen, the Bee Creek cave harvestman (Texella reddelli) and the Bone cave harvestman (Texella reyesi) are endangered.


We suggest you review the three categories of cave critters with this enthralling slideshow, "The Hidden Life of Caves," created by biologist Steven Taylor. Ask the kids, as you come to each new slide, "Does this look like a trogloxene, a troglophile, or a troglobite?" Ask them to support their guesses with what they have learned about each.

Click here


      When you discuss these endangered cave species, it's key that the children understand these are no ordinary endangered species. Endangered cave-dwellers are special cases because often a particular species has evolved for a particular cave. In other words, no other creature like it exists anywhere else except in that single cave!

We refer to this as a one-to-one relationship with the habitat and, as you can imagine, the absence of a single species in a very sensitive cave environment can have a domino effect on the other animals that live there too (this is particularly true of dark zones).

      One missing piece of the puzzle and the puzzle no longer can support all of the life it was meant to support. In an environment with such unique life forms which evolved to play such specific roles in the cave ecosystem, when one goes missing it can have devastating effects on the rest.

Please help the children "get" this: that it's not just about one "bug" going extinct. It's a much larger issue than that. The ramification of one bug going extinct is that the web of life has a broken link that can lead to more broken links.

In addition, below you’ll find, "Great Sources for Photos of Cave Critters," where we've listed two links that provide photographs so you can show your students what these unique animals look like.

      • Bee Creek Cave harvestman (Texella reddelli)
      • Texas blind salamander (Typhlomolge rathbuni)
      • This 1 minute video tells a bit about the Texas blind salamander: Blind Salamander (Typhlomolge rathbuni)
      • Bone Cave harvestman (Texella reyesi)
      • Coffin Cave mold beetle (Batrisodes texanus)
      • Kretchmarr Cave mold beetle (Texamaurops reddelli)
      • Tooth Cave ground beetle (Rhadine persephone)
      • Tooth Cave pseudoscorpion (Tartarocreagris texana)
      • Tooth Cave spider (Neoleptoneta myopica)

Great Sources for Photos of Cave Critters

Hook up the projector, make your classroom cave-dark then show the kiddos photos from these sites:




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