138 ENTOMOLOGICAL NEWS. [April, '06 



rated from the others by its appendages and the relatively 

 short hind wings (abdomen 36 mm.; h. w. 26 mm.). 



Somatochlora krcdsonica, alpestris, albidnda and probably dn- 

 gulata * form a group of closely related species with relatively 

 robust abdomens and long wings. Hndsonica finds its closest 

 ally in the European alpestris from which it is separated, 

 among other characters, by the great development of the basal 

 spine of the superior appendages. In alpestris the basal spine 

 and the spine following it are about equal in size, and the 

 profile view gives an accurate idea of the full size of these 

 spines. In its wing markings knd.s&nica is like septentrionalis. 



Albidnda is very distinct from the two preceding species ; 

 and dngulata is at once distinguished from them all by its larger 

 size and the broadly forked inferior appendages. The $ of 

 hudsonica from which the figure of the vulvar lamina was 

 drawn has the abdomen very flattened and the vulvar lamina 

 much pinched together, so the figure is probably somewhat 

 deceptive. The second 9 collected by Dr. Atkinson has the 

 last abdominal segments wanting. The vulvar laminae repre- 

 sented in figs. 20 and 21 are normal in shape, the abdomens 

 not being distorted. 



EXPLANATION OF PLATES V AND VI. 

 All specimens figured are in collection of E. B. Williamson. 



Fig. i. Appendages in profile of Somatochlora septentrionalis <j\ 

 Orono, Maine, June 18, 1898, Bartle Harvey, collector. This 

 specimen has the left superior appendage wanting and the 

 wings are in bad condition. 



Figs. 2, 3, 4, and 5 ; Somatochlora semicircularis. Figs. 2, 3, abdominal 

 appendages and 4, genital lobe of rj\ Manchester, Maine, July 

 7, 1898, Miss M. Wadsworth, coll. Fig. 5, superior append- 

 ages of cT, Langford Lake, British Columbia, July so, 1902, 

 R. C. Osburn, coll. 



Figs. 6, 7, and 8. Somatochlora arctica. Figs. 6 and 7 abdominal ap- 

 pendages and fig. 8, genital lobe of tf\ Leuzerheide, July, 1904, 

 K. J. Morton, collector. 



Figs. 9, 10, and n. Somatochlora forcipata. Figs. 9 and n, abdominal 

 appendages, and fig. 10, genital lobe of cf, Grand Lake, New- 

 foundland, July 21, 1901, D. A. Atkinson, collector. 



Figs. 12 and 13, Somatochlora alpestris abdominal appendages of <j\ 

 Leuzeiheide, July, 1904. K. J. Morton, collector. 



* Fi-ankliiii is known to me only from the description of the J . 



