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about the second week in July, though some of them will be found 

 full later than this and the insects do not all leave the galls at the 

 same time, for I have at the same time found galls in which a few 

 winged insects remained, others in which there were more and 

 others that were emptied. After the galls have been at least par- 

 tially empty the insects may be found on the twigs and at the ends 

 of the branches, though how permanently they locate there I do 

 not know. There is a gap yet to be filled in the history of the in- 

 sect between the third generation and the mouthless sexual indi- 

 viduals, the females of which so often perish while containing the 

 single winter eggs. Respecting this, Dr. Riley remarks, " I have 

 not been able to prove absolutely that there are two broods of the 

 gall-making female, and my observations all tend to the conclusion 

 that no galls are formed, except by the stem-mother that hatches 

 from the impregnated egg- I have never succeeded in obtaining 

 galls either by inclosing the winged females in muslin bags tied 

 on the living trees or by similarly enclosing her immediate pro- 

 geny, though I have succeeded in obtaining without any difficulty 

 an abundance of galls by so inclosing the stem-mother. Moreover, 

 all such succulent galls as this one are produced on the tender 

 leaves only, and I have failed to find them on any but those which 

 develop early in the season. It is true that we find the galls quite 

 fresh, and containing larvae, pupee, and winged insects as late as the 

 first week in July, and these late galls, as well as the insects within 

 them, are generally more yellowish than those found earlier in the 

 year ; but a careful study of the structure of the inmates shows 

 them to be identical with those found in the earlier galls; and 

 these late galls are from present knowledge to be attributed to the 

 work of late hatching and late developing stem-mothers, rather 

 than to the work of the third generation. I am inclined to 

 think that this third generation will be found to have a dif- 

 ferent habit ; possibly feeding upon some other part of the tree 

 without forming galls, and producing in time the true sexual in- 

 dividuals, something as in the case of Sc/i/zone?/ra americana.^^ 

 Bulletin U. S. Geol. Survey, Hayden, v, p. 12. While I would 

 not assume to present observations upon this species which should 

 be of the same value as those of so exceptionally skilful an inves- 

 tigator as Dr. Riley, I may yet add that my own investigations of 

 this species confirm the opinions expressed in the paragraph 

 quoted, and I do not at all believe that galls are produced by any 



