THE CLASS AND ORDERS OF INSECTS 187 



membranous, the forewing larger than the hindwing, which 

 is attached to it during flight by a row of hooks along the costa. 

 The first abdominal segment is annexed to the thorax. Cerci 

 are present, and the female's ovipositor is strongly developed. 



The larvae of Hymenoptera are of the cruciform type with 

 well-developed, mandibulate head. The pupa is " free ". 



Two sub-orders of Hymenoptera are recognized. 



Sub-Order i. Symphyta 



The Symphyta (saw-flies) have no constriction at the 

 base of the abdomen. The larva is usually a caterpillar 

 with three pairs of thoracic legs, and seven or eight pairs 

 of abdominal prolegs without hooks or spines. 



Sub-Order ii. Apocrita 



The Apocrita (gall-flies, ichneumon-flies, wasps, bees, 

 ants) have a marked constriction (" waist ") behind the 

 first abdominal segment. The larva is always a legless 

 grub. 



