GALL APHIDS OF THE ELM. 211 



some of the stem mothers are still plump and actively produc- 

 ing, in which case very young- nymphs occur in the gall together 

 with the newly winged forms not yet migrated, while other 

 stem mothers are much shrunken and no longer producing. On 

 June 19, 1909, most of the stem mothers were in the last instar 

 but not yet producing. 



Besides the stem mothers and migrating progeny there are 

 sometimes i or 2 apterous viviparous individuals in the gall. 

 (Figs. 133, 174, 175). The counts I made of Maine material 

 gave these at the rate of 2 for 13 galls. They were maturing 

 at the same time as the older of the migrants, — as was shown 

 by the embryos in their abdomens. What possible part these 

 forms play in the life history of the species I am unable even 

 to guess. There is the possibility that these are some distinct 

 species of aphid which has crowded into the opening of the 

 gall as guest. If so it is some species I have never taken in 

 any other connection. It is certainly desirable that nymphs pro- 

 duced by this form be reared through to the winged stage. 



The migrants after molting leave the gall through the open- 

 ing slit on ventral leaf. Their immediate fate has not been 

 followed but there is no doubt that they seek some species of 

 grass on which to deposit their young. It is indeed Tetraneura 

 graminis Monell which Mr. Monell has long considered to be 

 the grass form of Tetraneura colophoidea.^ 



From the Sirrine slides it seems likely that the nymphs live 

 upon the grass roots and that the pupae crawl up and settle upon 

 the grass blades before molting. 



The return migrants, according to the collection recorded by 

 Osborn-Sirrine, like those of Colopha ulmicola, seek the bark 

 of the elm in the fall and deposit the true sexes which produce 

 the winter eggs. "Winged forms of Tetraneura graminis were 

 found flying from Leersia zdrginica and at the same time winged 

 specimens of Tetraneura ulmi" (herez=colopJioidea) "were ob- 

 served alighting and hiding under rough bark of the elm; 

 where afterwards the peculiar males and females of the latter 

 were found as also the single egg of the female."* 



*This is the species suggested to be the same as graminis by Osborn- 

 Sirrine (1893) but as it was listed by them under the name of ul)iii this 

 record has been somewhat confusing. 



*Proc. la. Acad. Sci., Vol. I, Part 3, pp. 98-ior. 



