A centipede showing off its characteristic wriggling gait., Arcata.
The head of the centipede to the left. Note the black-tipped poison claws alongside the head.
Another centipede. (Lithobius sp.?), Arcata
Myriapoda (many-limbs) -- along with their more numerous relatives the insects, the arachnids, and the crustaceans -- are in the phylum Arthropoda (joint-limbs). Of at least a million identified species of arthropods, approximately 13,000 are myriapods. Though they represent only a small fraction of Arthropoda, myriapods are still three times more diverse than mammals.
Myriapoda are distinguished by their multiple segments and
single pair of antennae. Both centipedes (Chilopoda) and millipedes
(Diplopoda) are myriapods, as well as two smaller classes of arthropods
(Symphyla and Pauropoda). Of these classes, only the millipedes
have two pairs of legs per segment.
Centipedes have somewhat flattened bodies with a pair of legs
on every segment. The venomous ìfangsî are, in fact
claws attached to the first body segment that reach alongside
the head. Centipedes are typically born with all of their
segments in place and when they molt all of the segments expand
equally. Their reproductive organs are near the tail end
Scientists have identified around 3,000 species of centipedes.
| A centipede showing off its characteristic wriggling gait., Arcata. |
The head of the centipede to the left. Note the black-tipped poison claws alongside the head. |
| Another centipede. (Lithobius sp.?), Arcata |
Millipedes, in contrast to the flatter centipedes, have essentially cylindrical bodies. Variations include those with dome-shaped cross-sections, and those with flat projections appended to the top of the back. Local millipedes have 12 to 70 segments with two pairs of legs on each segment. The first four segments, however, have only three pairs of legs between them and several posterior segments have no legs at all. On mature males one pair of legs on the seventh segment is modified into gonopods, used for mating.
Young millipedes are typically born with only a few segments and then add new ones with each molt until they reach maturity. Tropical species of centipedes and millipedes can grow as large as 30 cmñ thatís a foot long!
Scientists have identified around 10,000 species of millipedes
Polydesmid millipedes have lateral projections on their backs, giving them a flattened appearance. Mature adults have 18-21 segments and are typically blind. Polydesmida is the largest order of millipedes with 2700 known species worldwide.
 Harpaphe telodonta (probably), Arcata |
 Harpaphe haydeniana, Humboldt Redwoods State Park |
 A small polydesmid, Patrick's Point State Park |
 Kepolydesmus sp.? mating, Arcata |
 Luminodesmus sequoiae, normal lighting* |
 Luminodesmus sequoiae, fluourescing under UV light.* |
Spirobolida is an order of large millipedes. Their bodies are usually "fat" relative to their overall length. The order Julida consist of smaller and skinnier millipedes. The two on the left are Spirobolid millipedes, the one on the right is Julid.
 Tylobolus?, (family Spirobolidae) Arcata. This one is 5 cm long (2 inches) |
 Cylindroiulus sp. (Fam. Julidae)??, Arcata. This is a tiny one: 9 mm long (1/3 inch) |
 Tylobolus?, (family Spirobolidae), San Francisco Peninsula. This is probably our largest local species: 10-15cm long (4-6 inches) with around 70 segments. |
Polyxenus sp., Arcata. Living in Redwood bark.
Although pill bugs and sowbugs are very similar to millipedes
in terms of diet, habitat, habits, and looks, they are not myriapods
at all, but rather they are crustaceans ñ together
with shrimp and lobster.
Adult females glowworms (beetles of the family
Phengodidae) retain their larval form and can be mistaken for
millipedes. To make matters worse, they eat millipedes by
biting off the head and eating their way through the body. If
you catch one of these beetles at the right time you will see
a millipede with one end glowing!
Female glowworm (Zarhipis sp.) in normal light and glowing
in the dark.
Photograph courtesy of Nancy Baumeister.
Last modified 27 November 2001
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