47 



occurs about Lake Talioe, Reno and Glen Brook, Nev. (Packard); ag4 

 was taken by myself sparingly at Beaver Brook and Morrison, Col. 

 Another species, which in allusion to its ashen tints is here called 

 M. cinereus, has been sent me from California and Nevada by Mr. 

 Edwards, and was taken by Dr. Packard at Wallula, W. T., and at 

 Reno, Nev., and by myself in great numbers at Great Salt Lake and 

 in the American Fork Canon, Utah. Possibly it is this species (I 

 have only poor specimens to judge from), which Capt. Pope took in 

 Texas, on the upper Pecos River. Finally the common M. femoratus 

 (Burm.) of the east, where it ranges liom Maine to N. Carolina, has 

 been found at Wallula (Packard), British Columbia (Crotch), and 

 the Shasta Valley (Edwards). 



The following table, based on the structure of the abdomen, may 

 serve to separate the males of these species. 



1. Penultimate segment of abdomen conspicuously inflated be- 

 neath 2. 



Penultimate segment of abdomen not conspicuously inflated 

 beneath M. collaris. 



2. Apex of last abdominal segment distinctly notched ... 3. 



" " " " entire or most obscurely 

 notched 5. 



3. Anal cerci broad, rarely nioi*e than three times as long as 

 broad, the apical half bent on the basal 4. 



Anal cerci slender, equal, straight, nearly four times as 

 long as broad M. devastator. 



4. Anal cerci more than twice as long as broad . . . M. atlantis. 



" " less " « " <' ... M. spretus. 



5. Anal cerci enlarged at the apex, the last segment of abdo- 

 men produced 6. 



Anal cerci tapering, or equal at the apex 8. 



6. Anal cerci strongly depressed, and a little twisted on apical 

 half M. cinereus. 



Anal cerci with apical half slightly bent, or in the same 

 plane with the base 7. 



7. Lower edge of anal cerci toothed M. femoratus. 



" " " " not toothed .... M. Packardi. 



