EXOPTERYGOTA 415 



These insects are widely distributed in the warmer parts of the 

 world. Many are gregarious, living in tunnels formed of silk pro- 

 duced by tarsal glands, e.g. Emhia major from the Himalayas. 



Order PSOCOPTERA (Booklice) 



Small insects, either winged or wingless; with biting mouth parts; 

 thoracic segments distinct ; wings with reduced venation from which 

 cross veins are largely absent; metamorphosis slight. 



These insects are to be found on bark and leaves of trees and feed 

 on lichens and dry vegetable matter. The eggs are laid on the bark 

 or leaves and covered by a protecting sheath of silk by the female, 

 e.g. Peripsocus phaep terus . 



Atropus pulsatoria, the booklouse, is found in damp dark rooms 

 and feeds on the paste of book bindings, wallpaper, etc. 



Order O DON AT A (Dragonflies) 



Predaceous insects with biting mouth parts; two similar pairs of 

 wings with characteristic reticulate venation; prominent eyes and 

 small antennae ; elongated abdomen with accessory male genitalia on 

 the 2nd and 3rd sterna; metamorphosis heterometabolous ; nymphs 

 aquatic, possessing a modified labium known as the mask. 



The members of this order are large insects, and in the Carboniferous 

 period genera existed which had a wing expanse of two feet. They 

 are strong and rapid fliers, catching their food in the form of small 

 insects, on the wing. The forwardly directed legs play an important 

 part in catching the prey and holding it while it is masticated by the 

 mouth parts. 



The thorax has a peculiar obliquity of form, the pleural sclerites 

 being directed downwards and forwards at each side with the result 

 that the leg bases are carried forwards towards the mouth and the 

 wing bases backwards. 



The wings (Fig. 308) have a complex venation of a reticular nature, 

 a stigma or chitinous thickening of the wing membrane found near 

 the apex being characteristic. There is no coupling apparatus. All 

 the mouth appendages are strongly toothed, maxillae and labium 

 assisting the mandibles more efficiently in mastication than in most 

 insects with biting mouth parts. 



Though the male pore is on segment 9 of the abdomen, the copu- 

 latory apparatus is found in the sternal region of segments 2 and 3. 

 Before copulation, spermatozoa are transferred to this apparatus. 

 The male then grasps the female in the region of the prothorax 

 by means of his posterior abdominal claspers. While in flight in this 

 tandem position the female turns her abdomen down and forwards 



