COMMUNITY OF PLAN IN INSECTS. 



149 



with sharp retractile claws. Such an animal as this is little 

 higher than some worms, and indeed is lower than many of them. 



We should also not pass over in silence the Centipedes (Fig. 

 178, Scolopocryptops sexspinosa) and Galley worms, or Thou- 

 sand legs and their allies (Myriopods), which by their long 

 slender bodies, and great number of segments and feet, vaguely 

 recall the worms. But they, with the mites, are true insects, as 

 they are born with only three pairs of feet, as are the mites and 

 ticks, and breathe by tracheae; and thus a common plan of 

 structure underlies the entire class of insects. 



A very strange Myriopod has been discovered by Sir John 



179. Young Pauvopus. 180. Spring-tail. i 81 . young Juhls. 



Lubbock in Europe, and we have been fortunate enough to find 

 a species in this country. It is the Pauropus. It consists, when 

 fully grown, of nine segments, exclusive of the head, bearing 

 nine pairs of feet. The young of Pauropus (Fig. 179) is born 

 with three pairs of feet, and in its general appearance reminds 

 us of a spring-tail (Fig. 180) as may be seen by a glance at the 

 cut. This six-legged form of Pauropus may also be compared 

 with the young galley worm (Fig. 181). 



Passing to the group of spiders and mites, we find that the 

 young mites when first hatched have but three pairs of feet, 

 while their parents have four, like the spiders. Figure 182 



