164 HYMENOPTEKA (SAWFLIES). 



Ichneumon and Saw-flies (Hymenoptera-terebrantia). 



The Ichneuinonidw (tig. 77, 5) and the TenthredinidcB are the 

 two families to be considered here. The former are entomo- 

 phagous — that is, parasitic in the larvae of other insects — and 

 with a stalked abdomen and projecting ovipositor in the female. 

 The chief families are — 



(i) The Pteroinalidcii, whose larvas are parasitic in various 

 insect larvaj and ova, and even in other parasites ; 



(ii) The BraconidcB, which attack caterpillars and beetle- 

 larvae ; and 



(iii) The IclmeumonidcE, which attack all larvae. 



The ova laid by these various insects hatch into little grabs, 

 which gradually devour their host, but not until they and their 

 host have nearly reached maturity, when they pupate either 

 within or external to their prey. The little yellow cocoons we 

 often see in abundance around the larvae of the Large Cabbage- 

 White (Pieris brassiere) in the autimm are the cocoons of one of 

 the Braconidffi, Mierof/aster (jlumeratus, which aids so much ia 

 destroying these noxious larvfe. on our cabbages. 



Ichneumonidffl vary much in size : some are microscopic, 

 while others are quite large. AU, however, are equally bene- 

 ficial, and worthy of our protection. 



The Hessian-fly is largelj"^ parasitised by these insects ; so are 

 Aphides. We can nearly always find some dead plant-lice on 

 every tree — pearly looking bodies, often with a minute round 

 hole, showing where the Ichneumon has escaped. 



The Sawflies and Wood-wasfs. 



Sawflies and Wood-wasps are phytophagous, with sessile ab- 

 domen, the larvae resembling caterpillars in the former group. 



(1) The Sawflies or Tenthredinida; have a sessile abdomen, 

 with short saw-like borer of a complex structure, which is only 

 exserted during egg-laying. The mandibles are well formed, but 



