SOME MIXED RELATIONSHIPS. 



79 



which, hatched in due season from the egg, passes its 

 early stages within the vegetable tissues. Out of the 

 gall, when its time arrives, the young gall-fly will issue 

 forth. Now, it is needless to say that, in bygone days, 

 zoologists very faithfully catalogued, defined, and de- 

 scribed the gall-fly family in all its branches. This 

 group of insects constitutes a well-known branch of the 

 great class of winged things. One might conclude, with 

 reason, that little was left to be desired in our know- 

 ledge of gall-fly habits or of gall-fly appearances. Yet, 

 as the sequel will show, the relationships of these 



Fig. 21. Gall insect (Cynips kollari), (i) natural size and (2) enlarged. 



estimable insects are getting decidedly " mixed," and 

 the increase of knowledge in this case is becoming, as 

 it too often does, an increase of sorrow to the other- 

 wise contented mind of the natural historian. 



The newer story of the gall-flies begins with the 

 observation that down in the roots of the oak-tree, and 

 in those parts of the roots which are but sparsely 

 covered with earth, there reside gall-insects of peculiar 

 kind. They come forth from their ground-galls as 

 wingless forms, and they are all mother-insects. It is 

 curious also to observe that they cannot reproduce the 



