154 ENTOMOLOGICAL NEWS. [Ma>% 



The species of insects which are able to produce galls are quite 

 numerous, and are found in nearly all the orders of this large 

 class, but these notes will, unless otherwise stated, refer in all 

 cases to such as belong to the order Hymenoptera, and to the 

 family Cynipidae. 



The species of galls produced by the Cynipidae are more 

 numerous on the oaks than on plants of any other order; indeed, 

 the oaks are noted the world over for the variety and abundance 

 of the galls they produce. Our North American oaks are known 

 to produce about two hundred species, and it is doubtful whether 

 one- half have yet been noticed. I have gathered, at one time, 

 from an oak standing alone in a cultivated field nine distinct 

 species. All trees of the sajne species are not equally the pro- 

 ducers of galls; indeed, of trees and shrubs whose branches in- 

 terlace, one may be infested with thousands of galls, while the 

 others produce none at all. Whether this is owing to what we 

 may call the individuality of the tree that is found to be favor- 

 able or otherwise — for trees of the same species have individual 

 traits, no two being alike — or whether a tree that the gall-flies 

 have once attacked is, thereafter, more susceptible to the influ- 

 ences that produces the galls, or whether it is due to entirely 

 different causes is not yet known. 



I have studied the oaks with special reference to this subject 

 and find that colonies of gall-flies are more or less persistent, 

 some having been known to me for fifteen or twenty years and 

 still existing. In one case I found that the Summer brood, 

 hatched from leaf-galls, laid its eggs for the next generation in 

 the bark of the large roots of the tree on which they grew, and 

 that when the insects from the root-galls appeared they laid their 

 eggs in the buds of the same tree. 



I have taken at one time, more than fifty of these last in the 

 act of egg-laying in the buds of two or three oak sprouts that 

 sprung from a common root and were not much higher than my 

 head. Other clumps of oak bushes a few feet distant furnished 

 none at all. 



This and some other facts of the same sort show that the female 

 gall-fly discerns a special fitness for her work in certain trees, but 

 does not show in what it consists. It is possible that the size and 

 shape of the oak buds, which differ considerably on different trees, 

 may have some influence in determining the insect's choice for 



