THE CLASS AND ORDERS OF INSECTS 181 



form, pass through no marked transformation, and, like 

 most exopterygote insects, are active throughout life. 



Sub-Order ii. Homoptera 



The Homoptera (cicads, froghoppers, snowy-flies, 

 aphids, coccids, etc.) have the rostrum inserted far back 

 close to the bases of the forelegs. The wings of both 

 pairs are often alike in texture and are held vertical or 

 sloping when at rest. 



Young Homoptera may resemble their parents closely 

 (aphids) or may differ from them markedly (cicads, 

 coccids). In the latter case there is usually a quiescent 

 final nymph-stage (so-called " pupa ") in the life-history. 



Order 13. Epherneroptera 



The Epherneroptera (mayflies) are delicate insects with short 

 feelers ; in the adult the jaws are reduced to mere vestiges so 

 that feeding is impossible. The wings are membranous with 

 complex netted nervuration, the forewing much longer and 

 broader than the hindwing. The elongate abdomen bears 

 long paired cerci, and often also a median tail-filament. The 

 paired genital ducts are entirely mesodermal. 



Mayflies have aquatic larvae with the crustacean type of 

 mandible, prominent maxillulae, and in addition to the tail 

 cerci, a series of paired abdominal appendages which are 

 modified into gills. The mature nymph on leaving the water 

 becomes changed into the sub-imago an instar with wings 

 capable of flight, but having to undergo a final moult before 

 the true imago is revealed. 



Order 14. Odonata 



The Odonata (dragon-flies) are strong, predaceous insects, 

 with short feelers, very prominent eyes, and formidable biting 

 mandibles and maxillae. The legs thrown forward under the 

 mouth serve as a fly-trap and the stiff, glassy wings, incapable 

 of folding are very similar in the two pairs. The elongate 

 abdomen has short, unjointed cerci and prominent reproductive 

 processes at the tail end. 



