CHAPTER XVI. 



MrRIAPODA. 



Class III. Myeiapoda (Gr. murios, countless ; podes, 

 feet). — This class is an extremely small one, -and includes only 

 the Centipedes and the Millipedes. In all the Myriapoda the 

 head is distinct, and not amalgamated with the thorax. There 

 is no clear boundary-line between the thorax and the ab- 

 domen, both being composed of nearly similar segments. The 

 body, with one exception, always consists of more than twenty 

 rings, and the hinder segments, which correspond to the ab- 

 domen, always carry locomotive appendages, whereas the 

 abdominal rings in Arachnida and Insecta are always des- 

 titute of locomotive appendages. One pair of antennae is 

 present, and the number of the legs is always more than eight 

 pairs. Respiration is carried on by branched air-tubes or 

 tracheae. 



In most of their characters the Myriapoda closely re- 

 semble the true insects, with which, indeed, they are not un- 

 commonly classed. The true insects, however, always have 

 the head, thorax, and abdomen, distinct from each other, and 

 have never more than three pairs of legs. In most of the 

 Myriapoda the young, or " larvee," are more like insects than 

 the adult, since they have only three pairs of legs, or are alto- 

 gether destitute of feet. In some cases, however, the young 

 Myriapod, on escaping from the egg, possesses nearly all the 

 characters of the parents, except that the number of body- 

 rings, and consequently of legs, is smaller, and increases with 

 every change of skin (" moult "). The class is divided into 

 two leading families, represented by the common Centipedes 

 and Millipedes. 



The Centipedes (Fig. 60) are carnivorous in their habits, 

 and the organs of the moutn are adapted for a life of rapine. 



