Hymenoptera 269 



Thus the two wings of each side are united so as to 

 present a single firm surface during flight. There 

 may be five longitudinal nervures (sub-costal, cubital, 

 and three anals) and these together with the cross- 

 nervules divide the wing into a moderate number of 

 cells. A tinted area the stigma is usually to be seen 

 towards the end of the costa ; below this is the 

 radial cell, beneath this several cubital cells, and 

 beneath these again several discals. The hind-body 

 has ten evident segments in the Sawflies, in other 

 families seven or eight, and in one four or five only 

 are recognisable. The tergite of each segment over- 

 laps the sternite. Throughout the order an ovi- 

 positor or a sting is well-developed in the females. 

 The head is very easily movable on the fore-body ; 

 the feelers are usually simple or clubbed, sometimes 

 angled (made up of scape and flagellum). Mandibles 

 are always present, but the form of the first maxills 

 varies greatly in the different families. Those of 

 Sawflies are not very unlike those of beetles, but in 

 the Bees they are modified into elaborate, kneading, 

 brushing and sucking- organs fsee pp. 77-8). 



Life-history and Habits. — The Hymenoptera 

 pass through a complete metamorphosis. The larva 

 is in all cases eruciform, but varies from a caterpillar 

 with numerous prolegs (among the Sawflies) to a 

 legless maggot (among the Ichneumons, Wasps, Ants 

 and Bees). The larval head is always developed, so 

 that the maggot never assumes the very degraded 

 form characteristic of the higher Diptera. The pupa 

 is free, the various organs of the imago being easily 

 recognisable in all cases, and is enclosed in a cocoon 

 spun by the larva, or sealed up in a cell by its parent 

 or nurse. Many instances of virgin reproduction occur 

 among the Hymenoptera. The higher families show 

 the greatest care for the young and the highest 



