go Thomas Albert Williams 



and lack of mealy substance in all forms. It is very agile and 

 when disturbed runs away rapidly and hides itself. 



Cotypes in the collection of the University of Nebraska (nos. 

 161, 162) and of the U. S. National Museum (nos. 36, 37, 148). 



EXPLANATION OF BIBLIOGRAPHICAL REFERENCES 



Bull. 111. Lab. Nat. Hist.— Bulletin of the Illinois State Labo- 

 ratory of Natural History. 



Bull. O. Ag. Exp. Sta. Tech. Ser. — Bulletin of the Ohio Agricul- 

 tural Experiment Station, Technical Series. 



Bull. U. S. Ent. Div. — Bulletin of the United States Department 

 of Agriculture, Division of Entomology. 



Bull. U. S. Geol. Sur. Ter. — Bulletin of the Geological and Geo- 

 graphical Survey of the Territories. 



Can. Ent. — Canadian Entomologist. 



Die Pflan. — Die Pflanzenlause Aphiden (C. L. Koch). 



Ent. Syst. — Systema Entomologiae (J. C. Fabricius). 



Fn. Boi. — Fauna Boica (Schrank). 



Fn. Sv. — Fauna Suecica (C. Linnaeus). 



Fourth Rep. St. Cab. Nat. Hist. — Fourth Annual Report of the 

 University of New York on the State Cabinet of Natural 

 History. 



Gli afidi, con un prospetto dei generi ed alcune specie nuove 

 italiane (G. Passerini). 



Guide to the Study of Insects (A. S. Packard). 



Horn. Brit. Mus. — Catalogue of the Homopterous Insects in the 

 British Museum (F. Walker). 



Ins. 111. — Report on the Noxious and Beneficial Insects of the 

 State of Illinois. 



Ins. Mo. — Report on the Noxious, Beneficial and other Insects of 

 the State of Missouri (C. V. Riley). 



Ins. N. Y. — Report on the Noxious, Beneficial and other Insects 

 of the State of New York (A. Fitch). 



List Aph. Minn. — List of the Aphididae of Minnesota, with De- 

 scriptions of Some New Species (O. W. Oestlund). 



174 



