OF WASHINGTON. VOLUME XIV, 1912. 103 



gation was made, October 4, 1911. The well in question was 

 found to be an ordinary dug well covered with a loose plank 

 platform and containing a pump. It was about 25 feet in 

 depth, partly bricked up and partly woodcased, and situated 

 on a side hill, where it undoubtedly received some surface 

 water, as was evident from the presence in the bottom of 

 the well of a considerable quantity of very fine clay silt such 

 as constituted the surface soil in the vicinity. The water, 

 which was 4 or 5 feet in depth, was reasonably clear at this 

 time, but possessed a ver} r faint odor. 



The householder stated that for several weeks he had been 

 compelled to strain the water through a cheese cloth in order 

 to rid it of these worms. Examination of the cloth tied over 

 the mouth of the pump at the time of my visit showed it to 

 contain a dozen or more that had been pumped up during the 

 previous half day. These were readily identified as the larvae 

 of a chironomid fly. 



A second visit to the well on November 15 showed the 

 larvsc still present in about the same numbers, and upon 

 lifting a board from the plank platform a number of small 

 midges were seen to escape. A careful scrutiny of the under- 

 side of the remaining boards resulted in the discovery of 

 numerous specimens, eight of which were captured. 



On November 23 several additional adults were taken and by 

 means of a dredge net over 50 of the larva? were secured. Al- 

 though special effort was made to secure eggs and p'upse, none 

 were obtained, owing probably to the lateness of the season. 



The captured larva-, which were all apparently nearly full 

 grown, were taken to the laboratory and placed in two sepa- 

 rate beakers of the well water, about equal numbers of larva- 

 in each. One beaker contained only the clear water, while in 

 the other a small amount of the fine clay silt from the bottom 

 of the well was placed. When placed in the water they im- 

 mediately began the peculiar and apparently useless opera- 

 tion, characteristic of chironomid larvre, of jerking the body 

 alternately from side to side, the tail touching the head first 

 on one side and then on the other. So far as could be observed 

 this movement served no useful purpose, since the insects 

 made no progress forwards or backwards by it. On the con- 

 trary, they sank straight to the bottom of the beaker. Here 

 their wiggling was of more avail, as in contact with tin glass 

 they were able to move awkwardly about. 



Somewhat to my surprise, it was soon evident that those in 

 the beaker containing the clay were not prospering. Their 

 constant wriggling tended to draw them down into the mud, 

 from which they were unable to extricate themselves. At 



