INSECUTOR INSCITI/E MENSTRUUS 81 



'Speaking especially of the Fallen Leaf Lake region, a region 

 in the heart of the Sierras to the north of the high peaks and 

 on the eastern side of the divide, A. taJiocnsis is the commonest 

 and earliest species, found everywhere, both in the hills and 

 the pines in level country. It breeds in the earliest pools of 

 clear water held in rocky land, its home being in the moun- 

 tains, but it soon spreads everywhere. It was common in the 

 early pools at the head of Fallen Leaf Lake, being often the 

 only species present. It also bred in wave-pools at the lower 

 end of the lake. Dispersal of the adults was in general down- 

 ward, they being abundant in the pines at Tallac on June 17, 

 though no breeding places were near. A. cataphylla is less 

 abundant and less widely dispersed at Fallen Leaf. It was 

 commonest at the foot of the trail to Angora Lakes at the head 

 of the lake, rare at the outlet of the lake and absent at Tallac 

 on Lake Tahoe. A. hexodontus breeds in early pools, but es- 

 pecially those of a marshy character, larvse being taken from 

 hoof-prints of cattle in the edge of a marsh. The adults were 

 well distributed and toward the end of June replaced A. 

 taJiocnsis as the dominant species. A. ventrovittis is a rare 

 species, taken only at one place near the outlet of Fallen Leaf 

 Lake and then in small numbers. It is presumably a marsh 

 breeder, though the larvae were not found. A. pahistris breeds 

 in open grassy marshes, not in large numbers. Dispersal was 

 general, adults being taken everywhere, although seldom com- 

 monly. A. increpitiis is the slowest breeder of any of the early 

 species, the larvae lingering after all the others are gone, fre- 

 quently in the same pools. The)^ were abundant at the outlet of 

 Fallen Leaf Lake with a downward dispersal, the adults being 

 common at Tallac, about 2 miles from the breeding places, 

 while only found a quarter of a mile up the lake and many days 

 later. 



The seasonal appearance of these mosquitoes varies with 

 the altitude in the ratio of about a month in time to 1,000 feet 

 of elevation. At Yosemite, at about 5,000 feet, all the species 

 were about a month earlier than at Lake Tahoe, at G,000 feet, 

 while at Summit, at 7,000 feet, they were still another month 



