THE CLASSIFICATION OF INSECTS 97 



whose larvae burrow into the stems of plants. The corn 

 saw-fly (Cepkus pygmceus) infests wheat, but is not 

 sufficiently common in this country to be injurious, though 

 on the Continent it is sometimes the cause of much 

 damage. 



The large wood-wasps (Siricidce) are represented in 

 Britain by two species : the giant wood-wasp (Sir ex gi gas) 

 and the steel-blue wood-wasp (S. juvencus). These insects 

 and their allies are characteristic of the northern forest 

 regions. By means of her powerful ovipositor, the female 

 inserts her eggs into the wood of trees, in which the 

 larvae burrow and feed. 



The true saw-flies (Tenthredirddas) are mostly of 

 moderate size. The ovipositor of the female consists of 

 two saw-like plates by means of which cuts are made 

 in the tissues of leaves and stems for the reception of the 

 eggs. The caterpillar-like larvae have many prolegs — 

 sometimes eight pairs. Most of them feed openly on 

 leaves, but a few species live in galls. The pupa is 

 enclosed in a tough, silken cocoon, which is generally 

 buried in the ground, but sometimes attached to the 

 food-plant. This family is characteristic of the northern 

 hemisphere, being poorly represented in tropical and 

 southern countries. 



Sub-Order 2. — Apocrita. 



In this sub-order, which comprises the vast majority 

 of Hymenopterous insects, the abdomen is markedly 

 constricted behind the first segment to form a waist. In 

 some families the ovipositor becomes a sting. In all 

 cases the larva is a white, legless grub which depends for 

 its sustenance upon the instinctive provision made by 

 the parent, or in the case of social species — upon the 



G 



