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, 1t 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. 
