CHAPTER II 



FISH-INSECTS, EARWIGS, COCKROACHES, AND 

 THEIR ALLIES 



THE first main group, or order, into which the 

 class Insecta (or Hexapoda) is divided is termed 

 Aptera. Its members are all tiny, wingless insects 

 with delicate biting mouth-parts. They undergo no 

 metamorphosis, the newly hatched young exactly 

 resembling the adults except in size. Whether the 

 Aptera are really " primitive " in the sense that they 

 have sustained little or no modification since they 

 branched off from the original ancestral stock, or 

 whether they once climbed to a high level of winged 

 efficiency and subsequently retrograded to their present 

 state, are moot points ; but they are certainly the 

 simplest of all living insects. Perhaps the best known 

 species is the little "silver fish," or "silver lady," 1 

 which is essentially a household insect, dwelling in 

 cupboards, boxes, and among shelving, where it feeds 

 upon a variety of vegetable substances, and at times 

 damages books, etc., by gnawing away the surface of 

 the paper. Its body aptly described as "carrot- 

 shaped " is completely covered with minute, silvery 

 scales. The pointed tail-end carries three long, slender 

 cerci, whence the name " bristle-tails " is often applied 

 to this insect and its near relatives. The antennae are 



1 Lepisma saccharina. 

 2 17 



