156 BRITISH APHIDES. 



jHerus querc/is and G. cori/li. After these larvee have 

 been struck by the fly they speedily turn to a shining 

 black colour. 



To this list of Chalcids may be added Ceraphron 

 Carpenteri, Curtis (Megaspilus), Encyrtus atheas, 

 Blassus parvicornis, which Walker thinks is equivalent 

 to Ephedrus, Westm., and Colax dispar of Curtis, 

 which may prove to be a Pteromalus. 



Mr. Walker informed me that he had bred Trioxys 

 and Ephedrus from Aphides. 



After an Aphis has been struck by an Allotria or 

 Aphidius it undergoes a peculiar change of form. 

 This alteration is even more remarkable if the Aphis 

 has succeeded in passing into the pupal stage 

 before the parasite wholly kills it. In both cases the 

 skin is hardened into a globular, shining, chitinous 

 or horny box, within which in some cases the transfor- 

 mation into the imago is effected, and out of which in 

 other cases the larva eats its way, in order to construct 

 the above-noticed tent. 



The Aphis sometimes dies only at the last phase of 

 its metamorphosis, for some pass out of the pupa 

 into a complete winged condition; but its fell 

 enemy has only delayed its action. In the case of 

 Coryna the tent under the abdomen gives a fanciful 

 resemblance to an ancient tilting casque. Such a 

 helmet is figured undter the imago of Siphonophora 

 rosa;, Plate LXIV, fig. 1. 



There scarcely seems to be a limit to the law that 

 the death of one is the life of another. On tearing 

 open one of these tent-like cocoons, eight or more 

 shining oval bodies were found, which I can only regard 

 as the pupae of some minnte Chalcid of a different kind. 

 As no Coryna grub was present, I could only suppose 

 that it had been consumed. Thus, there would seem 

 to be cases of parasites on the parasite of another 

 parasite of an Aphis ! We may ask where does this 

 series stop ? 



It cannot be doubted that atmospheric influences and 



