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Myriapods

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.

Class Chilopoda: Centipedes

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.

Class Diplopoda: Millipedes

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 cm-- that's a foot long!

Scientists have identified around 10,000 species of millipedes.

Subclass Chilognatha

Polydesmid Millipedes (flat-backed)

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.

* Photographed near Camp Nelson, Tulare County, California. Images courtesy of Osamu Shimomura.

Cylindrical Millipedes

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.

Diplopoda, Subclass Penicillata

Bristly Millipedes

Look-alikes

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 -- 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.

Return to Nature of the Northcoast: Millipedes

Written by Ari Kornfeld. Special thanks to Nancy Baumeister for help with taxonomic identifications and other details.

Photos courtesy of Ari Kornfeld (unless otherwise specified), copyright © 1996-2001. All rights reserved.