218 ELEMENTS OF COMPARATIVE ZOOLOGY. 



AMETABOLA. METABOLA. 



Thysanura. Coleoptera. 



Orthoptera. Neuroptera. 



Pseudoneuroptera. Hymenoptera. 



Hemiptera. Lepidoptera. 



Diptera. 



As will be seen from the foregoing tables, the group of 

 Hexapoda, or Insecta, is subdivided into nine groups or 

 orders.* 



ORDER I. THYSAKURA. 



These are small wingless insects without any general 

 common name except those of "bristle- 

 tails" and springtails, which have been 

 manufactured for them. The springtails 

 live in damp places in cellars, under 

 leaves in the forest, etc., and they have 

 a spring beneath the body by means of 

 which they can jump to great distances. 

 The bristletails have the body terminating 

 in two long filaments. To this last group 

 belong some pests known commonly as 

 "silverfish" soft-bodied shining forms, 

 which eat paper, starched clothing, etc. 

 FIG. 96. "silver- Aside from this silver-fish or "fish-moth" 



fish" (Lepisma , . . 



saccharina). the group has little general interest; but 



to the naturalist it is very interesting because it is so 

 primitive. 



ORDER II. ORTHOPTERA (see p. 181). 



* Many authorities recognize more orders than these, the difference 

 chiefly lying in the extent to which the Neuroptera and Pseudoneu- 

 roptera are subdivided. 



