120 INSECUTOR INSCITI^ MENSTRUUS 



Head hairs single; air-tube with 17 teeth, the last two or three de- 

 tached, the tuft arising beyond; lateral comb of eighth segment of 21 

 scales, each with a large central spine; anal segment not ringed by the 

 plate, which runs close to the ventral line. 



If the larva of spencerii were unknown, I should be in- 

 clined to assign this larva to it. As it is, further investiga- 

 tions must be made. I do not think the larva can be idaho- 

 ensis, which should be closer to spencerii than this is. There 

 is thus a fifth species, whether spencerii or not cannot yet be 

 said with certainty, breeding in irrigation water after the dis- 

 appearance of the early spring brood, but in negligible numbers. 



Aedes idahoensis Theobald. 



Very common on the limited prairie surrounded by mountains, 

 especially in western Montana. At Laurel females were 

 scarce, though males were still swarming, and the species 

 seemed to be disappearing. It was rare at Sandpoint, Idaho, 

 in forested country. All the specimens taken in western Mon- 

 tana have the abdomen with basal bands only. At Drummond 

 a few spenceriiAike forms were taken, as noted above. Farther 

 east the typical form obtained again. 



At Bozeman the males were observed swarming. I went 

 out toward the prairie at sunset, and, as the sun set, males 

 w re seen in a swarm over my head. The group would aug- 

 ment in number, then diminish, keeping about a foot overhead, 

 all the individuals facing toward a light breeze which blew 

 from the south. Two boys, perched on top of a water tank, 

 called out that there were mosquitoes up there, but they were 

 not bitten. The tank was at least 25 feet from the ground. 

 At the same time females were attempting to bite in the grass 

 about ankles and knees. At Laurel the males were repeatedly 

 seen swarming over low isolated bushes {Sarcobafus vermicu- 

 latus) in company with nigromaculis and curriei, but always 

 in separate swarms, each with its own relation to the bush. 



The species exhibits a certain variability. The intergrada- 

 tion toward spencerii in the Missouri valley has been noted. 

 The species also intergrades toward aldrichi at the timber in 

 the river valleys, which it invades to some extent. 



