Gall-FUes. 403 



able uniformity in the size of the gall apples ; for the punc- 

 tures and the eggs being uniform in size, and the gluten, by 

 supposition, uniform in quantity, no more than the same 

 quantity of sap can escape in such circumstances. 



But though this explanation appears to be plausible, it is 

 confessedly conjectural; for though Swammerdam detected 

 a gall-fly in the act of depositing her eggs, he did not attend 

 to this circumstance ; and in the instances which we have 

 observed, some unlucky accident always prevented us from 

 following up our observations. The indefatigable Eeaumur, 

 on one occasion, thought he would make sure of tracing the 

 steps of the process in the case of the gall-fly which pro- 

 duces the substance called bedeguar on the wild rose-tree. 



One of the bristles of the Bedeguar of the Hose magnified. 



and to which we shall presently advert. His plan was to 

 enclose in a box, in which a brood of flies had just been 

 produced from a bedeguar, a living branch from a wild 

 rose-tree ; but, to his great disappointment, no eggs were 

 laid, and no bedeguar formed. Upon further investigation, 

 he discovered that the brood of flies produced from the 

 bedegua? were not the genuine bedeguar insects at all, but 

 one of the parasite ichneumons (Callimone bedeguaris, STE- 

 PHENS), which had surreptitiously deposited their eggs there, 

 in order to supply their young with the bedeguar grubs, all 

 of which they appeared to have devoured. It may prove 

 interesting to look into the remarkable structure of the bede- 

 guar itself, which is very different from the globular galls 

 above described. 



The gall-fly of the willow (Cynips viminalis) deposits, as 

 we have just seen, only a single egg on one spot ; but the 

 bedeguar insect lays a large cluster of eggs on the extremity 

 of a growing branch of the wild rose-tree, making, probably. 



