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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



the sexual males and females, but not until the past summer has it 

 been definitely determined in what form this species appears upon the 

 cottonwoods early in the summer. Mr. Asa C. Maxson, in charge of 

 the experimental work in the Longmont district for the Great Western 

 Sugar Company, who has been a collaborator with us in some plant 

 louse studies, has succeeded the past summer in determining the form 

 of gall produced by this louse upon the cottonwood leaves and in suc- 

 cessfully colonizing the lice in large numbers upon the beets and in 

 rearing from these colonies, the sexuparse. We extract from a report 

 by Mr. Maxson upon his work as follows: ^'On May 4th . . . the 

 larvae were located upon the upper side of the leaf which was light in 

 color where the larvae were feeding, and showed a depression which, 

 as it grew larger, entirely inclosed the insect and formed a gall on the 

 under side of the leaf. This form of gall is produced by Pemphigus 

 halsamiferoe Williams."^ 



Many observations by the writers tend to confirm the conclusions 

 reached by Mr. Maxson whom we congratulate on the excellent life 

 history work that he has done on this insect, which is one of the worst 

 pests that the sugar beets have to contend against in the Rocky Moun- 

 tain States. 



It seems probable that Parker, in Jouenal of Economic Ento- 

 mology, 1914, page 139, hit upon the correct gall for this louse, but 

 referred to it on page 141 as by populicaulis Fitch, which produces a 

 globular gall upon the petiole of the leaf. Furthermore, this gall 

 occurs in the Middle and Eastern States, while P. hetce seems to be 

 strictly a Western species. 

 Pemphigus populicaulis Fitch 



Winter host, Populus species; alternate host unknown. 

 Pemphigus populitransversus Riley 



Winter host, Populus species; alternate host unknown. 

 Pemphigus populiramulorum Riley 



Winter host, Populus species; alternate host unknown. 

 Pemphigus ulmifusus Walsh 



Winter and early summer host, Ulmus species; alternate host un- 

 known. 



Mordwilkoja vagabunda Walsh 



Winter host, Populus species; late summer host unknown. 

 Asiphum pseudobyrsa Walsh 



Winter host, Populus species; alternate summer host unknown. 

 Asiphum sacculi Gillette 



Winter host, Populus tremuloides; alternate summer host unknown. 



1 Aphididse of Nebraska, Williams. University Studies, Vol. X, No. 2, 1910. 



