NOTES ON HYMENOPTERA. 63 



rience. I have, on previous occasions, bred many hundreds 

 of these gall-flies, but always from galls collected either in 

 September, October, or in early spring, and from such it 

 appears there is not the slightest chance of obtaining males. 

 1 own to being greatly disappointed this season, but the 

 failure, in my own case, may perhaps stimulate others to 

 follow up the subject, and I hope with better results. 



In breeding a large number of these gall-flies certain 

 phenomena present themselves, without offering, at the same 

 time, any obvious explanation ; at the same time, it is not 

 easy to suggest any probable cause for such circumstances. 

 In cutting open a number of galls, I found flies, one in about 

 a hundred, that were only half the normal size of the species ; 

 these are not examples from which a gradual scale of dimen- 

 sion can be traced up to the largest specimens; this dimi- 

 nution of size might reasonably have been expected to occur 

 in such flies as were developed from the smallest galls— but 

 such was not the case — several were found in full-sized £:alls. 

 Unless we seek for a solution of this circumstance in a sup- 

 position that the larva in such cases were arrested, whilst 

 feeding, through falling into an unhealthy condition, I am 

 at a loss to offer any other suggestion. When I first found 

 a minute fly of this kind, I certainly thought I had dis- 

 covered the male Cynips at last. I have still upwards of 

 2,000 galls containing Cynips, that is to say, exclusive of 

 such as have been attacked by parasites, of which I have 

 found two— the Callimome Devonienms, and an apparently 

 undescribed species of Decatoma — but none of the remaining 

 galls will produce males. Mr. Walsh informs us, that he 

 has bred thousands of flies from these old galls, which always 

 develope females ; such has always been my own experience, 

 and others have recorded similar results. 



Having alluded to parasitic Hymenopterous insects, it will 



