1917J Marchand — Notes on the Habits of the Snow-Fly (Chionea) 149 



glass cage had apparently become too high; however this may be, 

 the insect was found dead in the cage in the direct sunlight. The 

 other specimen had remained in the shade. In the evening, the 

 temperature fell to — 11° C, and being curious to know whether the 

 Chionea would withstand such low temperatures, I left the glass 

 door of the veranda open over night. On the morning of Decem- 

 ber 9, the second Chionea was dead, apparently killed by frost, 

 after the fashion of the famous tamed herring which had learned 

 to walk about and breathe air but one day fell into a pond and was 

 drowned. The adaptation to cold has evidently its limits even in 

 Chionea, and this insect, although it has its most active stage at 

 low temperatures, seems to withstand freezing less than many 

 other insects which at low temperatures become entirely passive. 

 The possibility that the males have normally a shorter life than 

 the females should, however, be taken into consideration, and may 

 partly account for their rapid death. The factor of humidity may 

 also be of importance, and death in the bright sunlight may be due 

 to increased evaporation as well as to the temperature. 



Conclusions. 



Chionea is not an accidental guest on the snow but perfectly 

 adapted to life on the snow by its habits. This is evident from the 

 fact that it can move about on snow for a practically indefinite 

 time without being frozen, while most other insects which may be 

 collected on the snow have been carried there by air currents or 

 attracted by the strong light, but do not run about on the snow 

 and usually perish within a few hours on the spot where they have 

 fallen. Furthermore, the Chionea regularly drinks water from 

 the snow by pressing its proboscis against it as was repeatedly 

 observed. 



Chionea is attracted to the snow: 



(1) By the bright light and white color of the snow (+phototro- 

 pism) ; 



(2) By a thermotropic reaction which is, in itself, stronger than 

 the phototropic reaction and which increases in the light ( — thermo- 

 tropism) ; 



(3) By the peculiar contact of the snow and a direct stimulus 

 resulting from the action of cold on the claws (special temperature- 

 sensibility?). 



