Arthropods at the Cofrin Center for Biodiversity

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Insects, Millipedes, Centipedes

Phylum: Mandibulata

Phylum Mandibulata are named after the characteristic mouthparts, mandibles, possessed by members of this group. These jaw-like structures work against one another to bite and chew in a manner similar to the jaws of mammals or the beak of birds. However, Mandibulata is an incredibly diverse group containing a huge number of species, some of whose mandibles have evolved into distinctly un-jawlike structures: Examples include the piercing/sucking mouthparts of mosquitoes and the sponging mouthparts of the housefly. These animals have highly modified mandibles, but they belong in the Mandibulata just the same. There are 2 subgroups (classes) within phylum Mandibulata.

Snails Class Myriapoda (Meer-ee-uh-poe'-duh)

The name of this class means "many feet," and myriapods all share this characteristic. Their bodies are made of a head followed by many similar segments each bearing one or two pairs of legs. Myriapods include centipedes, millipedes, and their relatives. Centipedes (order Chilopoda) have only one pair of legs per segment. They are all predators which use venomous fangs (which are not the mandibles but actually a modified pair of legs) to subdue their prey, including insects and other small animals. There are about 3,000 known species of centipedes. Most of them are ground-dwelling, and some are adapted for burrowing into soil, but a few are marine.

Millipedes have two pairs of legs per body segment. These animals use their mandibles to munch on organic detritus (although there are a few predaceous millipedes, too). Most millipedes live on the ground surface and are adapted for using their many legs to push their way or "bulldoze" through leaf litter. These animals do not have poison fangs, although many species have glands that secrete defensive chemicals, including cyanide-like compounds. There are more than 10,000 millipede species described so far.

Hexapod Class Hexapoda (Insects: Hex-uh-poe'-duh)

This is the largest class of animals, in terms of number of species: Nearly 1 million have so far been described, and several times that number remain unknown to science. Although only a few species are marine (and none have been found in the deep ocean), insects are dominant in almost every terrestrial and freshwater ecosystem, and they occupy nearly every ecological niche available to animals (herbivores, carnivores, internal and external parasites, detritivores, etc.). The name hexapoda means "six feet," a very familiar insect characteristic.

References

Margulis L, Schwartz KV (1998) Five kingdoms: an illustrated guide to the phyla of life on earth. 3rd ed WH Freeman, New York.

Pechenik, J. A. 2000. Biology of the Invertebrates, 4th ed. McGraw-Hill, New York.

Biodiversity Topics: Introduction . Plants . Animals . Mammals . Birds . Reptiles & Amphibians . Arthropods . Spiders . Insects