1911] MuttkowsM, Wisconsin DragonfUes. 31 



Here also the range in size is considerable. In an attempt to 

 correlate the females of hageni and ebrium with their respective 

 males, I find distinct color differences, which may be of service 

 in the determination of mutilated specimens. 



i. The orbicular spot on segment two of the abdomen is 

 mushroomed in hageni; always with a special point directed 

 basally in ebrium. Rarely pointed in hageni. 



2. The apical rings on segments three to six are rarely pointed 

 dorsally in hageni, nearly always in ebrium. Furthermore, when 

 viewed through a lense, ebrium nearly always (two partial, one 

 entire exception among twelve males) has a very fine dorsal line 

 leading from the dorsal point of the apical ring to the base of the 

 segment. 



3. Females of ebrium and hageni are said to be well-nigh in- 

 distinguishable. In the material before me the two species seem 

 to be distinct. Yet the distinctions are so trifling that I doubt 

 whether they are reliable. Besides, in the mass of material I 

 have only three undoubted pairs of hageni, and but one of ebrium, 

 so that the identity of the females referred to each species must 

 be regarded as tentative. 



I do not doubt that a correlation of the mesothoracic lamina 

 of the female to the form of the superior anal appendages of 

 the male will ultimately be discovered. Indeed, it would be 

 surprising if such were not the case. Mr. Williamson 3 has already 

 suggested as much. I have repeatedly tried to ascertain the exact 

 position of the male superior appendage on the female meso- 

 thorax, but such copulating pairs as I obtained thus far, had 

 always separated in the net before I could examine them more 

 carefully. 



Viewed from the mechanical standpoint, it would seem that 

 the male ebrium used its deeply bifid superior appendage as a vise, 

 or, at least, as a double lever which is much more effective than 

 the simple cylindrical process of hageni. 



4. In looking for venational differences between these two 

 species I was greatly surprised by the approximation of hageni 

 toward Ischnura.. For example, if we disregard the stigmal dif- 

 ference, Ischnura is distinguished from Bnallagma chiefly by the 

 origin of vein M„ — four cells beyond the nodus in the fore wing, 

 three cells in the hind wing, while in Bnallagma vein M 2 arises 

 at five and four cells, respectively, beyond the nodus, or more. 



3) Ent. News, Vol. 17, p. 144, 1906, U D. 



