706 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvii. 



specimens of this spet^ies from "White's Warm Springs, Saw Tooth, 

 Idaho. There are in the collection of the Illinois State Laboratory of 

 Natural History a number of specimens collected by Prof. S. A. Forbes 

 in the Yellowstone National Park, labeled "Firehole, Jul. 19th, 1890." 

 There is in the collection of Dr. O. S. Westcott, of Chicago, Illinois, a 

 single imago collected ]\v him in the Yellowstone Park. It will be 

 observed that these specimens, representing- the northernmost limit of 

 the known range of the species, come from warm water. Possibly this 

 species, which appears to be common in ordinary waters far to the 

 southward, is able to extend its rang-e through the agency of these 

 warm streams, which furnish the proper temperature conditions for 

 the development of its nymph. Possibly this is equall}^ the case with 

 Mesothemis. eolJocata. and with other species also. 



LIBELLULA FORENSIS Hagen. 



I have of this species a single female specimen that was bred h\ Mr. 

 S. Bethel, at Olympia, Washington, on May 2, 1898, and a number of 

 younger nymphs taken earlier in the season by the same collector. 

 The imago was placed in alcohol before transformation was complete, 

 and is in a very bad condition, and hardly determinable. It appears 

 to be the species named above, and the structural characters of the 

 nymph point to the same species. 



Length, 2-1 mm.; abdomen, 1.5 mm.; hind femur, 6.5 mm.; width of 

 head, 6.5 mm.; of abdomen, 7 mm. 



Body lanceolate, very hairy. Head compact, half as long as wide, 

 with small eyes capping the high anterolateral angles, little contracted 

 behind the eyes, where sides are nearly parallel to the broadly 

 rounded and scurfy pubescent hind angles. Antenna? about as long 

 as the head, the relative length of segments from base outward : 

 1:1:1.8:1:1.2:2:1.5. Hinge of labium reaching backward as far as 

 the mesothorax. Median lobe of mentum moderate, a toothlike pro- 

 longation in the middle of its front border, which is bordered with 

 spinules rather regularly placed, l)ut not crenate. Mental setfe about 

 8 each side in a short and sharp curve, all weak and fragile. Lateral 

 setse 6. Teeth about 10, low, subtruncate, subserrate, each armed with 

 three or four graduated spinules. 



Legs slender, very hairy. ^Mng cases reaching backward as far as 

 the base of the sixth abdominal segment. 



Abdomen lanceolate, widest on segment 6, and gradually tapering 

 thereafter to a long point. Dorsal hooks on segments 3-7, poorly 

 developed, except on middle segments, and hidden under thick tufts 

 of coarse hairs. Lateral spines on segments 8 and 9, short, sharp, 

 straight, about a fifth as long as their respective segments. Append- 

 ages longer than the long ninth and tenth segments together, slender, 

 sharp, fringed with tawn}^ hairs; laterals less than half as long as the 

 others. 



