2 Thomas Albert Williams 



scriptions, and these are herewith presented exactly as he left 

 them. 



In explanation of Mr. Williams' taxonomic methods it is nec- 

 essary to state that when he collected a number of aphids he 

 mounted them upon as many slides as it took to do so properly 

 and drew up his descriptions from these slides collectively, so 

 that each slide became in fact a cotype except in a few cases 

 where all the specimens were mounted upon a single slide and 

 consequently that slide became his type. Sometimes he marked 

 his slides of cotypes " types " and sometimes he omitted doing so. 

 Sometimes there are two or three slides of the same new species 

 all marked " type." Mr. Williams deposited nearly complete sets 

 of his material both in the collections of the University of Ne- 

 braska and in the United States National Museum, and the num- 

 bers referred to in designating type slides are those of these two 

 series which are numbered independently and in a different 

 sequence. 



In the " Host-Plant List " the following names were referred to 

 as representing new species : Pemphigus alnifoliae, oenotherae, 

 zvalshii; Lachnus fiocculosa, rileyi, smilacis; Callipterus ulmifolii; 

 Chaitophorus bruneri, cordatae, salicis; Aphis artemisicola, canae, 

 chrysanthemicola, cnici, lilicola, lonicericola, lugentis, partheno- 

 cissi, saniculae, sativae, scnecionis, solidaginifoliae, yuccicola; 

 Myzus oenotherae, potentillae, thalictri; Rhopalosiphum dianthi 

 poae; Siphonophora artemisicola, carnosa impatientis, chrysan- 

 themicolens, desmodii, eupatorii, gaurae, garrina, grindeliae, lu- 

 teola; Phorodon cyanoglossi, monardae ; Cryptosiphum canaden- 

 sis. In addition to these forms mentioned in the " Host-Plant 

 List," Mr. Williams discovered and described two other species, 

 Pemphigus balsamiferae and Aphis pentstemonis and specimens 

 of these species are in both collections. Of the species included 

 in the " Host-Plant List " one, Callipterus ulmifolii, had pre- 

 viously been described by Monell and was so regarded by Williams 

 in his thesis, its appearance in the " Host- Plant List " as a new 

 species being probably a lapsus pennae. The " Host-Plant List " 

 mentions Chaitophorus salicis and Pemphigus oenotherae as new 



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