20 



SCHOOL ENTOMOLOGY 



"hundred-legged worms" and " thousand-legged worms" 



or centipedes and millipedes. 



The centipedes have one pair of legs to each segment, 



are generally flattened 

 and have the legs at- 

 tached near the edges 

 of the segments. Mil- 

 lipedes are oval or cylin- 

 drical, have two pairs of 

 legs per segment and 

 have these attached near 

 the median line of the 

 segments on the under 

 side. Both forms have 

 one pair of antennae and 

 have bodies composed of 

 head and an unspecial- 

 ized chain of segments 

 representing thorax and 

 abdomen. 



Myriapoda are of 

 slight economic impor- 

 tance. Millipedes some- 

 times feed on vegetation 

 extensively enough to 

 be injurious, while cen- 

 tipedes are predaceou3 

 and feed mostly upon 

 insects. Some forms of 

 centipedes, especially in 

 tropical and subtropical 



countries, are provided with poison glands and may injure 



man seriously by their bites. 



Fia. 8. Some Relatives of Insects. 

 Reduced. 



a, the tailed Whip-scorpion (class Arach- 

 nida , order Pedipalpi) ; b, Harvestman 

 (Arachnida, Phalangidea) ; c, Spider (Arach- 

 nida, Araneida) ; d, Centipede (Myriapoda, 

 Chilopoda) ; e, Sow-bug or Pill-bug (Crustacea) 

 f, Millipede (Myriapoda, Chilognatha) ; g, 

 -fish ( 



Cray- 



(Crustacea). 



