Cave Pod People

The most common cave dwellers are those which are mostly ignored: the invertebrates. These exoskeletoned creatures include insects, water dwelling crustacea, spiders, and some just weird critters. One of the most complete inventories of cave and spring dwelling invertebrates was undertaken by James E. Gardner, then wildlife biologist for the Missouri Department of Conservation, from September 1978 to August 1984.

The result of his work, published as Invertebrate Fauna from Missouri Caves and Springs by the Conservation Commission in 1986, is the most complete listing of invertebrate cave species in Missouri between two covers. In it, Gardner describes 414 species including:"a horsehair worm, two flatworms, three leeches, 30 snails, 19 isopods (11 aquatic and eight terrestrial), 16 amphipods, nine crayfish, eight psuedoscorpions, five ticks, 11 harvestmen, 36 spiders, 18 centipedes, a symphylan, 18 millipedes, 42 springtails, five diplurans, three mayflies, a dragonfly, six crickets, 112 beetles, a psocid, eight hemipterans, a homopteran, two dobsonflies, 11 caddisflies, two stoneflies, nine moths, 25 flies, three fleas, and 5 hymenopterans."

Out of these, Gardner found 39 troglobitic varieties of cave dwellers, including isopods, amphipods, decapods, gastropods...you get the picture. Nearly every troglobite (except for a flatworm) has the word "pod" somewhere in its scientific description.

Voila. The Pod People. Rather than going into great detail on all 414 species (which took Gardner 72 pages, and whose book is highly recommended for people interested in such things) here are some of the highlights of cave invertebrates:

Cave Crayfish

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Two troglobitic Missouri species, the Salem Cave Crayfish, Cambarus hubrichti and the Bristly Cave Crayfish, Cambarus setosus. Both are blind, white, smaller and more slender than aboveground (epigean) crayfish. Another noticeable feature are the length of the antennae when compared to epigean species. They are supposed to survive to great ages, based on counts of annular rings, though some people believe these rings actually are counts of seasons of abundant food, not years. The Salem Cave Crayfish occurs mostly on the Salem Plateau, and the Bristly Cave Crayfish occurs mostly on the Springfield Plateau. These crayfish are commonly found in caves and springs containing the cavefishes, though it is not definitely known who is predator and who is prey in this relationship. Some biologists have put forward the theory, that in a cave ecosystem, sheer luck, speed and size, not preference, determines who gets eaten.

Isopods

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Isopods are a fairly common crustacean in caves, in both troglobitic and epigean forms. Some isopods are terrestrial, and some are aquatic. They vary from microscopic to one-half inch (1.4 cm) in size. They have segmented bodies, jointed legs, and vaguely resemble household silverfish. They are scroungers, living usually in the water or in guano piles, and feeding on microorganisms. Isopods can be plentiful in caves with a large food supply.

Amphipods

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Amphipods are also crustaceans, usually aquatic, which resemble tiny shrimp--a curled body with many joined legs beneath. The usually are found under the same conditions as aquatic isopods, but usually do not grow as large as them. Both troglobitic and epigean species exist. Both isopods and amphipods are part of the diet of cavefish, crayfish, and salamanders..

Cave Insects, Arachnids, and Their Relatives

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Among the most common insects and arthropods one runs into in Missouri caves are beetles, crickets, millipedes, centipedes, spiders and flies of various sorts. Some are troglobitic, some are merely epigean species which use the caves because they like the conditions. Most troglobitic insect species are noticeable smaller than their above ground counterparts. Scutigera, a large arthropod which looks like it escaped a Grade B movie set, are well known from Missouri caves. A large, fairly beautiful moth, Scoliopteryx libatrix overwinters in a few caves. Heliomyzid flies are very common in caves, and at one time or another, seem to be lunch for just about everyone. Of course, there is the webworm--the fungus gnat larvae who wrote this home page. And collembola, a primitive, fungus eating insect, which are everywhere rotting stuff is to be found.