CHAPTER XIII 



PARASlTlSM—coiiiinued 



Types of Life-Cycle. Group A, p. 331 ; 1. digestion of Parasite 

 Eggs by the Host, p. 331 ; 2. Types of Migratory Primary Larvce, p. 333 ; 

 3. Non-Migratory Primary Larvce, p. 336 ; Group B, p. 337 ; Group C, 

 p. 339 ; Group D, p. 340. Host Relations of Parasites, p. 343. 

 Hymenoptera, p. 344 ; Diptera, p. 351. Polyembryony and Related 

 Phenomena, p. 353.^ — (a) Chalcidoidea, p. 354 ; (b) Proctotrypoidea, 

 p. 356 ; (c) Ichneumonoidea, p. 358 ; {d) Vespoidea, p. 358 ; Origin of 

 Polyembryony, p. 358 ; The Embryonic Membranes, p. 359 ; Origin of 

 Mixed Broods of Parasites, p. 361. Adult Parasites. Feeding 

 Behaviour, p. 363 ; Phoresy, p. 364. Literature, p. 365. 



Types of Life -Cycle 



Probably no branch of entomology has grown so rapidly in 

 recent years as our knowledge of the biology of entomophagous 

 parasites. It has revealed an amazingly wide diversity of phases 

 in the life-cycle and of adaptations to different modes of life. 

 This subject has become too extensive to admit of discussion from 

 every aspect in a limited space, and it is only intended to lay the 

 more important facts before the reader in a summarised and 

 co-ordinated form. 



In a broad general way the life-cycles of parasitoid Diptera and 

 Hymenoptera may be grouped into four categories. 



Group A. The eggs, or more rarely the larvae, are not 

 deposited on the hosts, but in situations favourable to the 

 latter becoming infested. Post-embryonic development may 

 be either ecto- or endoparasitic. 



Group B. The eggs are deposited externally on the hosts 

 and an ectoparasitic life supervenes. 



Group C. The eggs or larvae are deposited externally on 

 the hosts, but the subsequent development is endoparasitic. 

 Group D, The whole parasitic life is endoparasitic from 



330 



