2434 The Zoologist— January, 1871. 



easily explains this disproportion. I have observed the following 

 parasites : — 



" 1. Pimpla graminelhe, Grav. The larva is so frequent in the 

 galls of Triticum repens that, without linowing the insect it pro- 

 duces, one would be tempted to regard it as the lawful owner. It 

 is a curious circumstance, and one which I have observed else- 

 where but very rarely, that this larva seems to derive the greater 

 part of its sustenance from the plant itself. This is a departure 

 from the ordinary laws which govern the economy of parasites, 

 but the exception appears to me incontestable, and several species 

 of very different genera furnish instances of it. Surprised to find 

 the larvae constantly alone in the tube of the galls, without being 

 able to find the slightest trace of those which I supjiosed had 

 served them for food, I repeated my researches at a lime of year 

 when I might hope to meet them still young. From the month of 

 August 1 have seen them in different stages of growth, often not 

 more than a third or even a quarter of their size when adult; but 

 here again there was not a vestige of the victim that I was looking 

 for. The larvos were found with the body extended in a straight 

 line in a hollow proportioned to their size and entirely filled by 

 them. The walls of this hollow were very fresh, and seemed to 

 have been quite recently begun. I observed also that very often 

 the larvee were placed upside down or with the head downwards, 

 and similarly I saw several of the nymphs in that jiosition. Having 

 regard to the absence of any victim whilst the larva is young and 

 growing, and to the augmentation of the cavity which encloses it 

 commensurate with its growth, it must be admitted that the larva 

 is phytophagous, at all events during a large portion of its existence. 

 However this may be, the insect which ])roduces the gall must have 

 perished in the first days after the hatching of the larva, or perhaps 

 even in the egg state. Have we not a parasitism analogous to that 

 observed in other cases, where one hostile larva consumes the pro- 

 vision destined for another whose death it causes in its cradle and 

 whose place it tal<es ? This appears ]n-obable. I have had the 

 opportunity of making a similar observation on a very pretty Chal- 

 cidian {Auloyynnuis Aceris, Forst.), which frequently inhabits the 

 round or crimplcd galls in the leaves of Acer pseudoplatanns 

 which Schrank attributes to his Cynips Aceris, an insect which that 

 author never saw, and which I have been unable to obtain, though 

 1 have carefully watched more than a thousand galls. 



