INSECTA : HYMENOPTERA 447 



should be first chosen for study which will lay their eggs on the 

 leaf-buds or bark of such young trees. The Spangle Gall would be 

 a good type to begin with. The galls should be collected in the 

 autumn after the leaves have fallen from the trees and the galls 

 are becoming detached from the leaves. They should be laid 

 on a pot half full of damp sand or earth, covered with moss, and 

 the pot then sunk in the earth out of doors, and covered with 

 the muslin-covered frame ; under these conditions the larvae will 

 winter within the gall, the flies emerging probably in April. As 

 soon as they appear, the flies should be transferred to the young 

 oak saplings, and watched closely, for they will almost immediately 

 begin to lay their eggs in the oak buds, piercing a hole with the 

 long ovipositor characteristic of Gall Wasps. The buds pricked 

 should be marked, and a watch kept on them as they unfold. It 

 will be found that in a large number there is no result, the 

 egg has apparently perished ; but in a few there will appear on the 

 leaf a new gall, the Currant Gall, which is the second generation 

 of the Spangle Gall. If these Currant Galls are collected in June and 

 carefully kept fresh on damp sand, the male and female flies of 

 this second generation will be obtained, and the females may be 

 watched later on, crawling over the young plant and laying their 

 eggs in the under surface of a leaf, as a result of which new Spangle 

 Galls will begin to appear in three or four weeks' time. 1 



4. Any other plant Galls found may be identified by reference 

 to British Plant Galls, by E. W. Swanton ; the life-histories of the 

 insects causing them should be worked out as far as possible. 



1 For these suggestions as to the rearing of Gall Wasps I am indebted to 

 Dr. Adler's most interesting book on Oak Galls and Gall Flies, in which details 

 as to the life-histories of all the common oak galls are given. 



