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ORDER— APTERA. 



(Silver Fish and Spring-tails.) 



"Aptera" means without wings, and this order 

 includes Silverfish and Spring-tails. (Plate 3, Figs. 

 I and 3.) 



These are very primitive insects, and are quite 

 destitute of wings during the whole length of their 

 life. They have not even rudimentary wings. 



They have three pairs of legs borne by the thor- 

 acic segments. The integument or outer covering 

 is very weak and soft, and the body is covered with 

 easily removed scales. They resemble the larvae 

 of some other insects, and adults can only be told 

 by their sizes, and the full development of their 

 parts, such as the number of joints of the antennae. 

 The ring-like segments of the body are very simi- 

 lar, the thoracic segments being broader and carry 

 the legs, but in some groups there is little differ- 

 ence between the segments of the* thorax and the 

 abdomen. 



The respiratory or breathing system is very sim- 

 ple, and, in some types, is very immature. The 

 long tracheal trunk lines, which occur in most in- 

 sects along the sides of the body, and from the la- 

 teral branches of which the spiracles open out, are 

 absent in some of these insects. 



The food of insects of the Order Aptera is de- 



