THE CANADIAN ENTOMOLOGIST 379 



have been conducted by the writer to indicate the nature of these 

 organs, but they appear in structure quite similar to the sensoria 

 of the antenna in the genus Aphis. They are small circular or 

 oval structures composed of an outer rim and a middle pore-like 

 centre. Each organ is often surrounded by an irregular or oval 

 area which is differentiated from the surrounding chitin. The 

 organs occur near the base of the wings on the thickened origin 

 of the subcosta and radius, scattered along the area between these 

 veins and on the trochanters and bases of the femora. None 

 seems to be present on other portions of the legs. The species 

 examined are arranged under their respective genera. 



Genus Lachniis. 



Besides the presence of many small pores near the base of the 

 femur in species of this genus, larger ones, more^or less tuberculate 

 are sometimes also present in ponderosa Wms. (fig. 39) and L. 

 sp. (fig. 40). Ciirvipes Patch (fig. 41) does not seem to possess 

 any of these large pores. Another species (fig. 32) shows a broken 

 group. Members of this genus also possess usually a group of 

 small pores near the base of the hind wing as in ciirvipes (fig. 42) 

 and ponderosa (fig. 43). 



Genus Essigella. 



Essigella californicus Essig. does not possess the group of 

 small pores present in species of Lachnus examined, but the femora 

 are provided with only two moderate  sized ones near the base 

 (fig- 44). 



Genus Symydohius 



S. ohlongus Heyden seems to have none of these organs upon 

 the wnngs. There are .three or four however upon the femur, and 

 about the same number upon the trochanter (fig. 20). 



Genus Myzocallis 



Members of this genus as well as other members of the tribe, 

 have as a rule only a few pores situated at the base of the femur, 

 for example, M. alnifolicB Fitch (fig. 47) and M. bella Walsh (fig. 

 48). They have no definite group on the wings but sometimes a 

 few scattered pores on the subcosta. 



Genus Drepanaphis. 



D. acerifolii Thos. possesses a few small pores upon the sub- 

 costa. On the femur there are usually two large pores which are 



