210 THE ENTOMOLOGIST. 



Colias hyale, Anthocharis belia, and others in which the fore 

 wings from the discal cell to the apex had changed to black. 

 But these species are normally already marked with black, while 

 in R. rliamni the black apical coloration marks a new depart- 

 ture in development. 



ON THE OVIPOSITION AND INCUBATION OF THE 

 ICHNEUMONID PANISCUS {PARABATUS) VIR- 

 GATUS, FouRC. 



By Eupert Stenton, F.E.S. 



I BELIEVE it is generally thought that when a female ichneu- 

 mon meets with a lepidopterous caterpillar fulfilling the neces- 

 sary qualifications to serve as a pabulum for its own larva, the 

 fate of that caterpillar is irrevocably sealed. Though this may 

 be true as a rule, it is by no means invariably the case when the 

 parasite is the above species and its intended victim Cheimatohia 

 boreata, for the latter can and does.fairly often come off victorious 

 in the encounter. 



In the first place, this caterpillar's habit of spinning together 

 leaves and living between them is its best possible protection 

 against an external parasite such as P. virgatus, which places its 

 ova on and not in its host, having no long ovipositor wherewith 

 to reach it in its habitation, and so evidently dependent on 

 coming across it in the open. It was on supplying captive 

 virgatus females on May 26th and onwards with boreata larvae 

 that I was able to witness the caterpillar's method of defence 

 when attacked away from its abode ; and on its tenacity in the 

 battle which then takes place depends with which shall lie the 

 victory. 



It is the ichneumon's endeavour to place the egg as near as 

 possible behind the head of its host, no doubt to prevent removal, 

 which I found could sometimes be done if put too far towards 

 the anal end. In this direction it faces after pouncing upon 

 the caterpllar, who almost invariably then seizes one of its 

 enemy's posterior legs ; this is its main defence, but it will also 

 lash itself to and fro and turn on its back, the parasite 

 gripping tightly hold with its mandibles. To obtain sufficient 

 force to drive in the ovipositor, or in a case like this merely to 

 expel the egg, I have noticed that a female ichneumon exerts a 

 strong upward pull, particularly with the powerful posterior legs, 

 corresponding to the force it is necessary to put into the down- 

 ward pressure of the abdomen, and so by holding one leg the 

 caterpillar destroys the even balance of power, and renders the 

 parasite utterly incapable of ovipositing. The matter is thus 

 reduced to one of endurance, and should the caterpillar prove to 



