THE PROCTOTRYPOID P^R^ SITES 



(Super-family Proctotrypoidea.) 



With the consideration of the insects of this group we fiist 

 meet with forms which were formerly grouped together in a sec- 

 tion called the Hymenoptera parasitica, the true parasitic Hymen- 

 optera. In the old system this included the families Ichneumonidae, 

 Braconidae, Chalcididae and Proctotrypidae. Other groups have 

 been added since, and entomologists now, following Ashmead, 

 consider the Proctotrypoidea, in spite of their invariably parasitic 

 habits, to be more closely allied to the Vespoidea and Cynipoidea 

 than to the Ichneumon flies and the Chalcis flies. This is un- 

 doubtedly true as to structure, and it will be remembered some 

 of the Vespoidea which we have just been considering are para- 

 sitic in their habits, while, as will be seen when we take up the 

 Cynipoidea, some of these insects too, although most of them 

 are gall-makers, are truly parasitic in their life. 



How internal parasites live. — The development of the larvae 

 of those parasitic insects which live within the bodies of other 

 insects has been the subject of much speculation and some in- 

 vestigation. How these creatures breathe, nourish themselves, 

 move, cast their skins, and pass their excrement have been mooted 

 points. Cuvier thought that these larvae breathe by placing their 

 spiracles in relation with those of the insect in which they live. 

 Ratzeburg showed that some of them have a curious caudal 

 appendage with very thin walls, and this he thought acted as a 

 blood gill, oxygen being gained through its walls from the puri- 

 fied blood of the host insect. Boisduval concluded that they do 

 not take nourishment through the mouth; that they do not 

 breathe, and that they void no excrement, the larvae being analo- 

 gous to the foetus in mammals, which lives the life of the mother. 

 Newport described the larvae of certain Ichneumon flies as having 

 no anus, the rectum and its orifice being rapidly developed at the 

 final molt of the larvae. The older authors thought that these 



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