PHYLUM ARTHROPODA. PERIPATUS, CENTIPEDES, AND MILLIPEDES 



225 



phylum Arthropoda very well, and are, 

 therefore, sometimes placed in a separate 

 phylum, 



CLASS CHILOPODA 



The Chilopoda are called centipedes (Fig. 

 126). The body is flattened dorsoventrally 

 and, in different species, consists of from 

 15 to 173 segments, each of which bears one 



pair of legs, except the first which has legs 

 modified as poison claws, and the last two, 

 which usually lack appendages. Their prey 

 consists of insects, worms, mollusks, and 

 other small animals which are killed with 

 their poison claws and then chewed with 

 their mandibles. The antennae are long, con- 

 sisting of at least 12 segments. The internal 

 anatomy of a common centipede is shown in 

 Fig. 127. 



Figure 126. Centipedes have many legs. In the East Indies there is a giant centipede nearly 

 a foot long. The photo shows a smaller form, common in the United States. (Courtesy of N.Y. 

 Zoological Society.) 



Centipedes are swift-moving creatures. 

 Many of them live under the bark of logs, 

 or under stones. Some of the poisonous 

 centipedes of tropical countries belong to 

 the genus Scolopendra. They may reach a 

 foot in length, and their bite is painful and 

 even dangerous to man. The common house 

 centipede (Scutigera) has 15 pairs of 

 very long legs, and lives in damp places such 

 as basements. It is not only harmless to man, 

 but really beneficial for it feeds on insects. 



CLASS DIPLOPODA 



The Diplopoda are the millipedes. The 

 body is subcylindrical and consists of from 

 about 25 to more than 100 segments, accord- 

 ing to the species (Fig. 128). All segments 



bear two pairs of legs except the thorax, on 

 which the number is reduced to one pair. 



The mouth parts are a pair of mandibles 

 and a pair of maxillae. One pair of short 

 antennae and clumps of simple eyes are 

 usually present. There are olfactory hairs on 

 the antennae and a series of scent glands that 

 secrete an objectionable fluid which is used 

 in defense. In fact, there is a species in 

 Micronesia that ejects for several inches 

 such a highly irritating fluid that it will 

 cause temporary blindness. The breathing 

 tubes (tracheae) are usually unbranched; 

 they develop in tufts from pouches which 

 open just in front of the legs. 



Millipedes move very slowly in spite of 

 their numerous legs. Some are able to roll 

 themselves into a spiral or ball. They live in 

 dark, moist places, and feed, principally, on 



