ORDERS OF INSECTS. 



169 



Order III Collembola. 



These are Apterous insects, which attach themselves to foreign 

 bodies by means of a ventral suctorial tube. They are commonly 

 called " Spring tails," in allusion to the fact that the abdomen 

 carries a long forked appendage, which is employed as an elastic 



Fig. 113. — Types of Aptera. A, PedUulus huvmnus capitis, one of the Aiwplura; B, 

 Docophorus hamat'us, one of the Bird-lice ; C, Campodea, (me of the Thysanura ; D, 

 Degseria, one of the Poduridce ; E, Scale of a Podurid, as seen under the micro- 

 scope ; F, Degeeria purpit/rascens. All the flgui'es are greatly enlarged. (After 

 Packard and Gervais.) 



spring, and which enables the insect to effect extensive leaps (fig. 

 1 13, D and F). The best-known members of the gi'oup are the Podurce-, 

 which are generally found in moist dark places in gardens and in 

 similar situations. 



Order IV. THrsANURA. 



This order comprises insects such as Lepisma and Campodea (fig. 

 113, C), which are nearly related to the preceding, but are distin- 

 guished by the possession of a masticatory mouth, and by the fact 



