Spiders and Their Near Relatives 



vegetable matter. They are harmless, except that occasionally 

 they feed on growing plants. 



III. Class Chilopoda (Chi-lop'o-da). — The Chilopoda in- 

 cludes the centipedes. These, like the millipedes, are air-breathing 



and have an elongated body composed of 

 similar segments (Fig. 7). They can be 

 distinguished from the millipedes by the 

 fact that each segment bears only a single 

 pair of legs. The body is usually flat- 

 tened, and the antenna? are usually long 

 and many-jointed. 



. The centipedes are predaceous, feed- 

 ing on insects; they are common under 

 stones and other objects lying on the 

 ground. Many species are venomous. 

 The poison glands open through the claws 

 of the first pair of legs, which are bent 

 forward so as to act with the mouth-parts. 

 These creatures abound in all parts of 

 the United States; those that are found 

 in the North are comparatively small, and 

 Fig. 7. a centipede rarely, if ever, inflict serious injury to man; 



but the larger species, which occur in warmer regions, are said to 



be extremely venomous. 



Formerly the millipedes and the 



centipedes were grouped together as the 



Class Myriapoda (Myr-i-ap'o-da); and 



this grouping is retained in many recent 



zoologies. 



IV. Class Hexapoda (Hex-ap'o-da). — 

 The class Hexapoda comprises the various 



orders of insects. The members of this class 

 are air-breathing arthropods, with distinct 

 head, thorax, and abdomen. They have 

 one pair of antennas, three pairs of legs, 

 and usually one or two pairs of wings in 

 the adult state (Fig. 8). 



Among the more familiar examples of insects are grass- 

 hoppers, dragon-flies, butterflies, moths, and beetles. 

 There are so many excellent popular works treating 



6 



Fig. 8. AN INSECT; A 

 WASP, WITH THE HEAD, 

 THORAX AND ABDO- 

 MEN SEPARATED 

 /, thorax a, abdomen 



