VALUE OF A KNOWLEDGE OF ENTOMOLOGY 5 



Myriopoda (Tlwiisand-lcggcd zvorms). — These creatures are 

 known to most persons, and are divided into two orders: The 

 Centipedes constitute a group in which each segment bears 

 only a single pair of legs, while the body is generally flattened, 

 and the antennae are long with many joints. They live mostly 

 by preying upon other insects. The Millipedes (fig. 6) have two 



Fig. 6.— Myriopod. Enlarged 



pairs of legs to each segment except the first three ; the body is 

 more or less cylindrical, and the antennae are shorter with few 

 joints. Most species feed upon decomposing vegetable matter, 

 but some attack growing plants, more particularly those of 

 the garden and greenhouse. Injury by these creatures, how- 

 ever, is frequently exaggerated, as in the case of the sow- 

 bugs, previously mentioned. 



Hexapoda (Insects). — This brings us to the true insects 

 which are distinguished from the other three classes that have 

 been mentioned by having the 

 body divided into three distinct 

 portions, — head, thorax (chest), 

 and abdomen (belly) (fig. 7). 

 They have a single pair of an- 

 tennae or feelers, normally three 

 pairs of legs, and in the mature 

 stage, one or two pairs of wings 

 (save in exceptional cases). In 

 our present advanced state of 

 knowledge of the classification 



of true insects they have been divided into no less than nine- 

 teen^ orders, but for present purposes what is known as the 



1 For a list of these orders the reader is referred to pp. 77-81 of Comstock's 

 Manual for the Study of Insects, Comstock Publishing Co., Ithaca, N. Y. 



Fig. y.—Polfstes bellicosus. Somewhat 

 enlarged. (Marx del, U. S. Dept. Agr.) 



