Pomona Collkok .Iuuhnai. of Entomulooy 



713 



Sli/lc- Sliort. v.'irialilr in sli.-ipi', iisiiiilly liliint at tip. 



I'roin tlii-sf fffiicrnl clinniftcrs it will hi- st-rii that this trihf iiicliicli-s vrry 

 diverse eleiiients. However this may seem, from the vtTV lie^iiiniii); of thi" work 

 on Aphididif in America this partieiilar trihe has almost entirely lieeii thrown 

 into two genera, or I might say into but one. since the genus Sipha claims hut 

 few species. This geinis is of course I'liailoiihorun KiK-h. The typical .Vinerirnn 

 species, and so recorded hy I'rof. Oestlund (List Minn, .\phid.. p. 18, I8H(),) 

 has long heen the type for comparing most of the species helonging in the above 

 tribe, without paying much ,'ittenlion to the origin.al Kuropenn type or enileavor- 



Figure 229. Galls of Pemphigus populicaulis Fitch 

 Split to show the >;rcat niiiiihcr oi inhahit.inis. 



itig to separate the widely varying forms into new genera. I'rof. II. !•". Wilson 

 in the Canadian Kntomologist. Vol. XI. II. necemhcr. IfJIO. pages .S8i to .S88. 

 has taken the Hrsl step in the direction of revision by creating a new g«'nus. 

 Thomasia, out of what has been considered the .Vmerican type form for the genus 

 <'haitoplioriis. 



If one attempts to ni;ike .iny extensive determinations of tin- various species 

 of this tribe by means of the literature of today, he cannot but have it forcibly 

 brought to his mind, how poor the descriptions really are, and how difficult it is to 

 accurately place .-i new insect even in the right gemis. This is. of course, largely 



