1917] Marchand — Notes on the Habits of the Snow-Fly (Chionea) 145 



earth. It went on the snow but soon passed over to the sifted 

 earth without apparently showing any preference for either, the 

 temperature being low; running for awhile over the earth on which, 

 on account of its brownish color, it was hardly visible, it passed 

 again on the snow and ran there approximately as long as it had 

 on the earth. It then started, with some effort, to climb the 

 glass walls of the cage, demonstrating the negative geotropism of 

 most insects, and arrived on the wire-netting of the cover. In the 

 arrangement described, it was found that the Chionea preferred 

 the uncovered part of the wire-netting where the open air had 

 access. Apparently it was seeking out the coldest spot available. 



It was observed that each time when, in the course of running 

 about on the wire-cover, it approached the part which was covered 

 by a glass plate it stopped its straightforward course, running 

 alongside the covered part and soon returned into the open region. 

 Several times it went under the glass cover as if for trial, but never 

 remained very long; while in the open region it would run about 

 freely in various directions. 



It was not ascertained with exactness how long the insect stayed 

 in the covered nor how long in the open part, but the observations 

 clearly show that the Chionea preferred the open region, which 

 seemed to indicate that it found here its apparently very low 

 optimum of temperature. The cage was exposed to the open air 

 at not much above freezing temperature, in a glass veranda, the 

 door of which was kept open. 



It was found that this behavior of the Chionea was somewhat 

 modified by the influence of light. On that side of cage which was 

 in greater distance from the light, it went more often under the 

 covering glass than on the side nearer to the light. It seemed 

 therefore that the negative thermotropism was stronger and more 

 pronounced in the light than in the shade. 



At the same time the Chionea showed itself distinctly positive 

 phototropic. The conflict between the two instincts must be 

 strongest on the side nearer the light, as here one should expect 

 the insect, on account of its phototropism, to go under the glass 

 cover. However, it is in the light, that it most consistently avoids 

 going under the shelter. As a result, its favorite place remained 

 that part of the open region which was nearest the light and just 

 bordering the glass cover, and it was here that the fly usually came 

 to rest. 



