[ 456 J 3G 



them exhibit the rudimental wing-cases upon their backs, which show 

 that they have passed into the pupa state, and by the middle of this 

 month, most of tliem have become developed into perfectly winged in- 

 dividuals, changing at the same time from pale-greenish to a dingy blue- 

 black color. We will'not occupy space by a minute description of these 

 insects, inasmuch as, like the majority of gall-making insects, they are 

 much more easily recognized by the size, shape, and situation of their 

 galls, than by minute details of their own structure. 



Like other insects with wingless females, this species is much restric- 

 ted in its range, and it is common to see some trees damaged by them 

 and others not, though growing side by side. The infested trees are 

 easily distinguished from the others, at a distance, in the latter part of 

 the season, by the faded and yellow color of the foliage, especially on 

 the lower branches. 



If the lips which form the mouths of these galls be drawn apart, 

 any time in the month of June, and usually through the greater part of 

 July, they are found to be tilled with lice in all the stages of their 

 growth,- seeming to show that there must be a continuous generation of 

 them, or that the different broods interlock with each other. I have 

 found galls thus occupied even as late as the middle of August. 



In the same cavity, and intermingled with the insects, are usually to 

 be seen a considerable number of little spherical globules, varying from 

 the size of a very small pin-head to that of a ver^^ large one, sometimes 

 lying lose in the cavity, and at other times attached to the bodies of 

 the young lice, and usually adhering to the tips of their abdomens. 

 When one of these galls is opened, its crowded population are evidently 

 much agitated by the unwonted admission of light. Whilst watchujg 

 them attentively at such times, I have seen the curious spectacle of the 

 little globules flying out of the cell with such rapidity that the eye 

 barely caught a glimpse of them as they passed. I observed them 

 closely for a considerable time before I could get any clue to the mecha- 

 nicism by which this phenomenon was produced ; but I concluded that 

 it was caused by a jerking motion of the legs of the young lice. The 

 difficulty of determining this point lay in the suddeiniess and rapidity 

 of the motion, and the impossibility of knowing beforehand upon which 

 globule to fix the attention. 



Tliese globules are composed of a limpid fluid, not distinguishable 

 from water, covered with a film so exceedingly delicate that when sha- 

 ken out of the cell upon a hard surface, they break from their own 

 weight. Whether these globules occur in other galls I am unable to 

 say, but I have seen similar bodies in the cavities caused by the folding 

 of the edge of the leaf of the persimmon, produced by a species of 

 Psvlla. 



