250 



ANNUL AT A, 



infest- iii^iips. Many of the Hymenoptera have a sting at 

 the hind eid-^qf the abdomen. This is modified from the 

 ovipositor whici^^ in its turn is comparable with the gonapo- 

 physes of the coc:iT7$)a^qh. In the saw-flies the ovipositor is 

 in the form of a pair ot' v-^ws which are used for perforating 

 holes in twigs, in which the eggs are deposited. 



Order III. — Diptera, 

 Fig. 169. — Tsetse Fly {Glossina morsitans) x 3. 



The deadly African fly. 



The Diptera have a full metamorphosis, the mouth parts 

 adapted for *' piercing and sucking," and there is a single 

 pair of membranous wings. The hind wings are reduced 

 to a pair of small halteres or balancers, processes with 

 knobs. They comprise the Flies, Gnats and Fleas. 



Fig. 170. — Syrphus Pyrastri. 



A fly (A) whose larva (B) feeds upon the green aphis ; C is the pupa. 



