EMERY: SIMULIUM VITTATUM IN KANSAS. 329 



The following number of Simulinm flies were trapped in the 

 Little Arkansas river at Wichita, Kan. : 



Nov. 10 12 flies. 



11 5 " 



12 33 " 



13 20 " 



Simulium flies may emerge during a warm spell in the 

 winter, as our experiments in December, 1912, show. My 

 field notes read as follows: "Dec. 11, Wichita, Kan. — Took 50 

 to 60 S. pupje from partly frozen river and placed them in a 

 laboratory, using city water. Dec. 12. — 14 S. flies emerged. 

 Dec. 13. — 10 S. flies emerged." 



A moderate or cool temperature seems to aflFect not only the 

 length of an individual S. vittatinn fly's life, but also its biting 

 habits or blood-thirsty nature. "If cold weather follows their 

 appearance, the gnats become semidormant; they are not 

 killed by it nor by rain, but revive and become aggressive again 

 with the first rays of the sun. Hot weather, however, soon 

 kills them."' 



During the months of September and October, 1911, we used 

 over 1200 flies in our experiments with pellagra. Not until the 

 cooler weather, the later part of October, did we succeed in 

 getting the flies to bite. At this time the temperature was about 

 20° cooler than when they had refused to bite. According to 

 the local U. S. government weather station, the temperatui'e 

 frequently ran above 90° in September, with an average maxi- 

 mum of 86.1° and minimum of 65.7°, while in October, at the 

 time of biting, the maximum was 67° and the minimuin was 

 45° F. Again in the middle of November the following year, 

 1912, I caught S. vittatiun at Wichita, carried them over 150 

 miles to Topeka, and succeeded in getting them to bite. One 

 month later I took Simulium pupje from the Little Arkansas 

 river, which was partly frozen over, placed them in a labora- 

 tory with water running over them at a temperature of 60° F., 

 and secured twenty-four flies. They were then taken about 

 200 miles to Parsons, where we succeeded in getting four of 

 them to bite a supposed case of pellagra. (Only sixteen flies, 

 one-half of which were males, made the trip). 



Before this time I had supposed that perhaps the flies had to 

 oviposit before they would bite, but from the above experi- 



1. Dept. Agri, 1886. 



