GALL APHIDS OF THE ELM. 229. 



There seems to be but one significant point not entirely settled 

 in Riley's life-cycle account, and that is the natural location of 

 the fourth generation (i. e., the progeny of the spring migrants). 

 Without definitely proving it he states that "we may rest pretty 

 confident" that the pseudova of the winged mother are consigned 

 both to the leaves and to the twigs, for he says that this fourth 

 generation may be found on the tender leaf-stem or in the mid- 

 rib on the under side. But of especial interest is his statement, 

 "They are, however, able to sustain themselves on the tender 

 bark of the twigs alone, and may be found nearly full grown, 

 there exposed to view and enveloped in the white cottony mat- 

 ter, which brushes off at the slightest touch." 



Although I have no definite proof, it is my belief that Schizo- 

 neura rileyi as common with us in the tender bark of young elms 

 is the summer form of americana. I can find no stable char- 

 acter to separate rileyi from americana and have for several 

 years believed them to be the same species. Professor Gillette 

 (1909) states that he "inclines to believe the two forms are 

 one species" because he is unable to separate them with any 

 certainty.''' 



Riley figures the antenna of the second generation with 5 seg- 

 ments and states that the 5th is the counterpart of the 2nd gen- 

 eration. A collection of 5 apterous viviparous forms taken from 

 the elm leaf curl, July 16, 1909, all had antenna 6-jointed. Fig. 



154- 



Prof. J. M. Aldrich (1901) gives a very important record of 

 the spring and return migration of amerieana: 



"Some of the specimens in the leaves develop wings and fly to new 

 locations during the earlj^ part of the summer; and about midsummer all 

 the rest do the same, so the old leaf-nests are deserted. Where they 

 go has not yet been found out. There is a closely related form in Eu- 

 rope that migrates to grass and it is probable that ours do the same. 



"In September the return migration takes place. Last year it was a 

 very conspicuous affair in Moscow, as all the trees, of whatever kind 

 were surrounded by a hovering swarm of delicate, winged lice. These 

 return migrants do not eat anything, and after a few days their dead 

 bodies were very abundant on the trunks of many trees, filling the 



is 3, while in Iloniiaphis there are but 2. The fact that in Sc. americana 

 there are 4 is therefore interesting, and of some value in this connec- 

 tion." 



*Notice, also, the connnent on ScIiiconcKra fodicus Buckton, p. 233 of 

 this bulletin. 



