CHAPTER IV. 



Order I.— THYSANURA.* 

 [Bristle-tails, Spring-tails, Fish-moths, et al.) 



The members of this order are wingless insects which undergo no 

 metamorphosis, the larval form being retained by the adult. The 

 mandibles and maxilUc are retracted within the cavity of the head, 

 so that only their apices are visible; they have, however, some freedom 

 of motion, and can be used for biting and chewing soft substances. 

 True compound eyes arc rarely present ; but in some genera there is a 

 group of agglomerated simple eyes on each side of the head. The 

 abdomen is sometimes furnished with rudimentary legs ; and in one 

 genus there arc well-developed abdominal legs. 



This order comprises chiefly minute insects, which live on decay- 

 ing vegetable matter, and can be found 

 abundantly in damp situations ; some 

 species, however, live in warm and dry 

 places, and feed upon starched clothing, 

 the binding of books, and other dry 

 substances. In the more common spe- 

 cies, the body is either elongated, and 

 furnished with six well-developed legs, 

 and two or more long, many-jointed, 

 caudal appendages (Fig. 56) ; or short, 



Fig. 56. — Lepisma. saccharina. 

 (After Lubbock.) 



FlG. 57. — Papirius fuscus. (After 

 Lubbock.) 



thick, and with a forked springing apparatus, bent under the 

 abdomen, instead of the thread-like caudal appendages (Fig. S7>- 



* Thysanfira: thysanos (-Bvcravo?), a tassel; oura (ovpd), the tail. 



