ORDER I. THYSANURA. 



This order is placed in the centre in our graphic 

 arrangement as the survivor of the main stock of 

 wingless forms, A. It includes the most generalized 

 insects, and is represented in the Guide by Campodea 

 and Lepisma. 



CAMPODE.E. 



Campodea (Fig. 27, enlarged) is only about one- 

 sixth of an inch in length, so that it is too small for 

 satisfactory class-work. It is found under stones and 

 in damp places. Here we have a long, cylindrical, and 

 hairy body, of nearly equal breadth throughout, divided 

 into three distinct regions, two of which, the thoracic 

 and abdominal, are again divided into definite and 

 movable rings. The number of these rings — three 

 thoracic {b', b", d'") and ten abdominal c^-c^^ — is easily 

 determined, as there is little concentration of parts. 

 The head (^) is without eyes, but possesses a pair of 

 long, finely developed antennae {at), which under the 

 microscope bristle with hairs. On the terminal section 

 there is, according to Kingsley,^ a possible sense organ 

 which resembles a couple of beans placed side by 

 side, and which is supphed with the tip of the anten- 

 nal nerve. It may be a fact of some significance, as 



1 Science Record, February 15, 1884. 

 64 



