GALL- APHIDES. 



393 



new colonies; and, during their migrations, attract 

 the attention of the most incurious by the singularity 

 of their appearance.* 



Oalls produced on the leaves and leafstalks of the Poplar by 

 Briosoma populi, with the various frrms of the insects, winged, 

 not winged, and covered with wool, both of the natural size and 

 magnified. 



On the black poplar there may be found, later in 

 the season than the preceding, a gall of a very dif- 

 ferent form, though, like the other, it is for the most 

 part on the leaf-stalk. The latter sort of galls are 

 of a spiral form ; and though they are closed, they 

 open upon slight pressure, and appear to be formed 

 of two laminae, twisted so as to unite. It is at this 

 * J. It. 



