226 



ELEMENTARY ZOOLOGY 



CLASS MYRIAPODA : THE MYRIAPODS, OR CENTIPEDS 



AND MlLLIPEDS. 



Belonging to the branch Arthropoda, with the classes 

 Crustacea and Insecta, are three other classes, of which 

 one, the Onychophora, is represented by a single genus 

 Peripatus (Fig. 85), of extremely interesting animals. 

 However, as these animals are not found 

 in the United States we cannot study 

 them. The other two classes are the 

 Myriapoda, including the centipeds and 

 millipeds or thousand-legged worms, and 

 the Arachnida, including the scorpions, 

 spiders, mites, and ticks. All these 

 animals are often spoken of as insects, 

 but though related to them they are not 

 true insects. 



TECHNICAL NOTE. From under stones or 

 logs obtain specimens of millipeds, or thousand- 

 legged worms (large blackish, cylindrical, worm- 

 like animals with each body-segment back of the 

 fourth bearing two pairs of jointed legs) ; also 

 specimens of centipeds or hundred-legged worms 

 (flattened, usually brownish or pale worm-like 

 animals with the body-segments bearing only one 

 pair of legs each) in the same places. Examine 

 the external structure ; note number of body- 

 rings ; division into body-regions ; presence of 

 FIG. 85. Peripatus antennae; character and number of eyes; charac- 

 eiseni (Mexico), ter of mouth-parts ; character and arrangement 

 (From specimen.) o f j e g S> j n tne centipeds the first pair of legs is 

 modified to form a pair of poison-fangs. They appear to belong to 

 the mouth-parts. The internal anatomy will be found to be, if 

 examined, much like that of insects and can be studied from the 

 account of the anatomy of the water-scavenger beetle and butterfly 

 larva. Compare the Myriapods with the Hexapods or true insects. 

 What are the points of resemblance ? what are the points of differ- 

 ence ? 



The Myriapoda are land-animals breathing by means 

 of tracheae like the insects. In them the body-segments 



