THE ENTOMOLOGIST. 551 



I reared still greater numbers, male and female, from enor- 

 mously swollen petioles of leaves of the same tree. These 

 two broods are remarkably alike, so much so that I could not 

 separate them if mixed. There is, in this instance, no per- 

 ceptible difference in the size of the individuals composing 

 the two broods. It seems to me to be settled now that most, 

 if not all, our species of Cynips are double-brooded, and 

 that one of these generations consists of females only. 

 Besides the two cases I have mentioned, where the con- 

 nexion between the two broods is apparently well established, 

 there are so many one-gendered species that we may reason- 

 ably suppose each to be the progenitor of some one of the 

 equally numerous double-gendered species, but whose rela- 

 tionships have not yet been observed. I am willing to venture 

 the remark that probably no one-gendered species exists — 

 that those apparently unisexual species, C. q. -punctata, 

 Bassett, C. q.-spongifica, Osten-Sacken, and those European 

 species whix;h, though reared in countless numbers, have as 

 yet been found only in the female sex, will be found to be 

 double-brooded species, one of which will be exclusively 

 female, and the other male and female. 1 have two or three 

 years tried to raise a colony of C. q.-punctata, Bassett, by 

 placing the large polythalamous galls on uninfected trees just 

 as the insects were ready to escape. So far I have failed to 

 rear any galls of this species. Now if these females really 

 reproduce the same kind of gall I ought to have succeeded, 

 for I colonized several hundred individuals on a single small 

 tree, and many more on other trees in different seasons. Of 

 course the inference to be drawn from the failure of my 

 attempt to raise these galls has no scientific value, but had I 

 succeeded in raising the galls the fact would have been 

 received as satisfactory proof that these female flies could 

 produce generation after generation of females without the aid 

 of the male element. I take the ground that the reproduction 

 of gall-insects without the intervention of the male is limited 

 to a very few, if not even to one generation ; and that all our 

 unisexual species are dimorphic forms of double-gendered 

 species. I wish yourself and all others interested in working 

 out the singular history of this family would give attention to 

 these points. And may I ask you to inform me if anything 

 has been written within a year or two that throws any light 



