THE CANADIAN ENTOMOLOGIST 243 



A considerable number of arthropod sare recorded as having been taken 

 on the snow, including mites and spiders and members of almost every order 

 of insects. The occurrence of a good many of these creatures, however, is 

 purely accidental and involuntary, and is due to their having been evicted in 

 some way from their winter shelters. On the other hand, others come out 

 regularly and with intent, or, if you prefer, as the result of some tropism. But 

 with the doubtful exception of Isotoma saltans Ag., reported from the glaciers 

 of the Swiss Alps, no hexapod, so far as I know, makes its permanent habitat 

 on the snow. There are some micrcscopic rotifers and some curious worms 

 (01igocha?ta) that seem actually to live and breed in the snow of glaciers, but 

 the snow- frequenting hexapods merely emerge from the soil and surface detritus 

 for a few hours, mere cr less, and those that do not perish on or in the snow, 

 eventually retire again to their subnivean shelters. In this class may be 

 mentioned in addition to the Collembola, the Mecopter genus Boreus, and 

 some of the stone- flies, (Plecoptera). I have seen thousands of the latter coming 

 out of the Madawaska River at Arnprior about neon on a fine day in March, 

 and all setting off southwards in obedience to a positive heliotropism that 

 headed them straight into the sunlight. But the best known and most regular 

 frequenters of the snow are certain species of Collembola. 



The term "snow-flea" is sometimes used as if it designated a single species. 

 Doubtless the title was first applied to Achorutes socialis Uzel, by far the most 

 frequent and abundant species on the snow. But it is necessary nowadays to 

 widen the application of the name; for at least eight genera of Collembola 

 including more than thirty species, have been recorded as appearing on the 

 snow in Europe and North America. Here again, however, we must distinguish 

 between mere chance appearances and regular occurrences. Authors generally 

 have paid little or no attention to this point, but there is no doubt that a good 

 many springtail species appear on the snow, not in the course of a normal life 

 activity, but as the result of an accident. Of the eleven species I have collected 

 on the snow in the vicinity of Arnprior, four had obviously fallen out of logs or 

 been washed from the ground by the running water of a thaw, and the individuals 

 were either dead or numb with cold, although at the same time, the hardier 

 species were quite active on the surface. But even allowing this, the Collem- 

 bola have still a far larger number of snow species, both actual and proportional, 

 than any other order of insects. 



It is remarkable that practically all the snow habitues among the spring- 

 tails belong to the more primitive of the two sub-orders; the Arthropleona. 

 The only record I can find of a Symphypleona on the snow is given by Schott, 

 who speaks of Sminthiiriis aureus Lubb. as having so occurred in Sweden. But 

 while he mentions no date, the context 'of his statement leads to the suspicion 

 that the snow fall was an unseasonably early one, and that the creatures were 

 there by accident. 



It is also worth noting that, so far as my observations go, none of the white 

 or light-coloured species ever come out in the winter. The snow frequenters 

 are of various shades of blues, browns, yellows, reds, greens and purples, but the 

 colours are all so dark that nearly all the insects Icok virtually black on the 

 snow. The ^celebrated Count Rumford, giving practical effect to his studies 



