THE CANADIAN ENTOMOLOGIST 365 



ON THE AMERICAN REPRESENTATIVES OF SOMATO- 



CHLORA ARCTICA WITH DESCRIPTIONS OF TWO 



NEW SPECIES. (ODONATA). 



BY E. M. WALKER, TORONTO. 



Three North American species of Somatochlora have been 

 described in which the appendages of the male are of the same 

 general form as in the palaearctic species S. arctica Zetterst. These 

 are S. forcipata Scudd., S. semicircular is Selys, and S. franklini 

 Selys. Another species, 5. macrotona, has been described by 

 Williamson (Ent. News, XX, 1909, pp. 78-79) but, as mentioned 

 below, I find this to be identical with franklini. To these three 

 species I have two others to add, so that we have in North America 

 five species of the arctica group. I had intended that the descrip- 

 tions of these new species should first appear in a monograph of 

 the American species of this genus, which is now in course of 

 preparation, but at the request of another writer who wishes to 

 list one of them I decided to publish them in advance. 



The five North American species of Somatochlora of the 

 arctica group may be separated as follows: 



A. Superior appendages of cf with a prominent external tubercle 

 beyond the middle, visible from above; vulvar lamina half 

 as long as 9th sternite, bilobed ; postclypeus wholly 

 black semicircularis Selys. 



AA. Distal external tubercle of superior appendages when 

 present not or scarcely visible from above; vulvar lamina 

 little or no shorter than the 9th sternite, entire; postclypeus 

 variable. 



B. Abdominal segments 5 to 7 with yellow latero-basal spots, 

 greatest width of cf abdomen distal end of seg. 5, thence 

 narrowing caudad. 



C. Lateral thoracic spots brownish, scarcely paler than 

 the ground colour, the mesepimeral elongate, ill de- 

 fined; superior appendages of cf in profile straight, 

 ventro-lateral tooth not affecting the outline; vulvar 

 lamina extending almost or quite to the hind margin 

 of 10th sternite incurvate n. sp. 



November, 1918 



