emery: SIMULIUM VITTATUM in KANSAS. 339 



hence against the current. This would frequently delay the 

 downstream journey of the fly, and occasionally long enough 

 for safety." 



Mr. Williams said he saw a hydrobatid suck the life blood out 

 of a fly. Here we have fish and beetles preying upon the adults 

 and larvae. 



METHODS OF CATCHING AND HANDLING SIMULIUM FLIES. 



Trapping Simnlinm flies is an interesting proposition from 

 the nature of their habits and habitat. Ordinarily we can 

 catch a great many kinds of insects with a net. In the case 

 of SimitUitm flies, unless they are in swarms or are very nu- 

 merous over the water, it is difficult to get many of them that 

 way. 



In order to carry on our experiments it was necessary to 

 have them alive and in large numbers. Swarms of them were 

 not to be found, and only a very few individuals were hovering 

 over the ripples at any time. We at once decided to trap them 

 in the ripples as they emerged from their pupse, and thereby 

 secure flies free from any contagion that might interfere with 

 our experiments. 



On account of the habits of the pupse requiring simply mois- 

 ture to keep their gills wet, I had good success getting the 

 flies to emerge by placing stones with pupte on them in straight 

 running water, and then setting a trap over them. The trap 

 consisted of a small wooden box about one foot deep, one and 

 one-half feet wide, and two feet long, without a top. This was 

 turned bottom side up and a hole eight inches in diameter cut 

 in it. In this hole I tacked a cone made out of window screen- 

 ing covered with cheese cloth. Then by cutting notches in the 

 ends of the box to let the water run through without leaving a 

 hole for the flies to crawl out, the trap was complete. The box 

 being dark inside, the flies upon emerging came up into the 

 light in the cone and rested on the inside of it. Plate XXXVIII, 

 figure 3, shows the structure of such a trap. 



At first I tried the screening alone without covering it with 

 cloth, but the flies crawled through the meshes and escaped. 

 Another thing I tried was a small screen cone inside a larger 

 cone, like one sees in traps used nowadays to catch house flies, 

 but this inner cone was useless because the Simulium flies 

 dropped back through the opening in the top of it when I tried 

 to take them from the outer cone. 



