62 HYMENOPTERA. 



he kindly forwarded to me, at the same time giving an ac- 

 count of the course to be pursued in order to secure a chance 

 of obtaining males. It is necessary, in the first place, to 

 obtain a large quantity of the galls just at the time when 

 they are becoming hard and woody, before a single fly has 

 arrived at maturity — certainly before any have escaped from 

 the galls. For three successive years I have searched for 

 such an opportunity, and this summer it fortunately occurred 

 to me. Last summer I visited Ilfracombe, and, in a wood 

 about two miles from that place, I found a part that had 

 been cleared of the trees and underwood ; I observed many 

 stumps of oaks, from which vigorous shoots were springing, 

 but not a single gall was to be found on them at that time. 

 This summer I visited the wood again, and was delighted 

 to see an abundance of galls ; when I first saw them they 

 were green and pulpy— this was at the beginning of Au- 

 gust. As I intended remaining the entire month at Ilfra- 

 combe, I felt assured that I had di-opt upon a golden oppor- 

 tunity for investigation. I watched the galls occasionally, 

 until I found, on opening a few, that the perfect insects 

 might shortly be expected to issue from them. I then com- 

 menced collecting and securing them in a number of fine net 

 bags — in all, I collected 4,410 galls. During the third week 

 of August the flies began to appear, and from that time up 

 to the beginning of November they continued to do so, in 

 greater or less numbers, this being accelerated or retarded 

 by the warmth or coolness of the temperature. Out of the 

 4,410 galls only 1,562 gall-flies have been developed, the 

 whole being of the female sex. 



Mr. Walsh informed me, that he had some seasons 

 bred as many as 2,000 flies, all of which proved to be 

 females ; for, he added, males do not appear to be developed 

 every season — such had been the result of his own expe- 



