EMERY: SIMULIUM VITTATUM IN KANSAS. 327 



places. The turkey gnat {S. meriocUonale Riley) appears 

 usually later, although in 1886 it appeared near Memphis, 

 Tenn., as early as April 5. The swarms were quite local, how- 

 ever, and strictly confined to the vicinity of the creeks that 

 produced them. The greater majority of the species of this 

 genus are northern insects, and appear there in the winged 

 foi-m all through the summer. The larv« require cold water 

 for development. As we go farther south the cold water can 

 only be found in the more elevated regions or in winter or in 

 the earlier months of spring. Earliness of season or high al- 

 titude are the substitutes for the lower temperature of the 

 more northern latitude." All this goes to show that the time 

 of the appearance of SimuUum broods varies with different 

 species and in different states. 



That S. rittatnm emerges throughout the summer is shown 

 from my field notes on that species in our experiments to de- 

 termine whether or not it is capable of transmitting the dis- 

 ease pellagra. We collected pupte as they formed on the rocks, 

 and placed them under a trap which was over the ripples so 

 as to secure as many flies as possible (fig. 1). The following 

 dates show uneven emergence of the flies from the breeding 

 traps and how they increase in numbers as cooler weather ap- 

 proaches, until the creek freezes : 



Oswego, Kan., 1911. 



