Pomona College Journal of Entomology 



713 



Stt/U' — Sliort, variable in shape, usually blunt at tip. 



From these general characters it will be seen that this tribe ineludes very 

 diverse elements. However this may seem, from the very beftiiiniiifj; of the work 

 on Apiiididae in America this particular tribe has almost entirely been thrown 

 into two genera, or I miglit say into but one, since the genus Sipha claims but 

 few species. This geinis is of course Cliaitophoriis Koeli. The tyi>ical American 

 species, and so recorded by Prof. Oestlund (List Minn. A])liid., j). IS, 1886,) 

 has long been the type for comparing most of the species belonging in the above 

 tribe, without paying uuich attention to the original Kuropean type or endeavor- 



Figure 229. Galls of Pemphigus populicaulis Fitch 

 Split to sliow tlie great number of inliabitauts. 



ing to separate the widely varying forms into new genera. Prof. H. F. Wilson 

 in the Canadian Entomologist, Vol. XLII, December, 1910, pages 384 to 388, 

 has taken the first step in the direction of revision by creating a new genus, 

 Thomasia, out of what has been considered tlie American type form for the genus 

 Chaitophorus. 



If one attempts to make any extensive determinations of the various species 

 of this tribe bj' 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 a new insect even in the right genus. This is, of course, largely 



