384 THE CANADIAN ENTOMOLOGIST 



Genus Thecabius. 

 Thecabius affinis shows a large group arranged in more or 

 less of a row near the base of the fore wing. Two or three only 

 are present near the base of the femur (Fig. 13). 



Genus Pemphigus. 



Several species of this genus were studied and they all showed 

 a considerable number of pores. P. populicaulis Fitch has a 

 series of nine or ten at the base of the hind wing (Fig. 5), and 

 about three on the fore wing. The base of the femur in this 

 species is armed with a group of five or six and two or three are 

 present on the trochanter (Fig. 6). Another species of this genus 

 taken in Colorado shows a similar group, but about a dozen are . 

 present on the fore wing (Fig. 7). These are surrounded by oval 

 or elongate transparent areas (Fig. 8). The individuals of this 

 second species were taken underground. 



Genus Colopha. 



C. ulmicola Fitch possesses a group of five or six in an even 

 row near the base of the fore wing (Fig. 16). 



Genus Hormaphis. 



H. hamamelidis Fitch, possesses a series of abolit a dozen 

 small pores. Scattered near the base of the wing none was ob- 

 served on the legs. 



Genus Phylloxera. 



Two species of this genus were examined, caryacaulis Fitch 

 and caslanece Hald. Both showed the same character of the 

 grouping of the pores. These occurred near the base of the fore 

 wing in a rather compact group, carycecaidis (Fig. 1) and castanea 

 (Fig. 2). The legs seem to show no small pores, but some speci- 

 mens of caslanece possess one large pore (Fig. 3). 



It will be seen from the foregoing tabulation that species 

 living underground and those inhabiting galls possess upon 

 their wings more of these structures than the free-living solitary 

 forms. In fact many of the latter have none upon the wings at 

 all. This applies also to those present upon the legs. Species 

 living underground possess them, as a rule, in more abundance 

 than their near relatives which are not subterranean. This will 

 be noted in the genus Aphis. In some genera, however, such 

 as the genus Lachnus, the aerial forms have these structures in 

 quite large numbers on the legs. 



