230 SNOW-FLY. 



may cause the various tumors found in our rodents, such as 

 the hares, squirrels, and gophers. The study of such flies is 

 a very interesting one, but for many reasons one full of diffi- 

 culties, apparently unsurmountable. Many interesting facts 

 can still be discovered in this field, and it seems strange that 

 thus far so very little has been done in tracing the life-his- 

 tories of the American species of these insects. 



Many other internal parasites are found in our domesti- 

 cated animals, such as Round-worms, Flat-worms, Leeches 

 and others, but to discuss and describe them, and to give 

 the proper remedies, is the work of the veterinarian. 



THE SNOW-FLY. 



( Vh'wnea valga Harr.). 



It is the general opinion that with cold weather all in- 

 sects disappear. This is true to a certain extent, yet there 

 are a fairly large number of exceptions which are very inter- 

 esting on account of being found at such times. As far as the 

 globe has been explored in the north, just so far have insects 

 been found, and not alone during summer and in well-shel- 

 tered spots but even in winter. The illustrations given in 

 figs. 188 and 189 (plate XVI) show the male and female of 

 a fly which is found in our state about Christmas, and as 

 far as observed only after a fresh fall of snow. Owing to 

 the whiteness of this material the insects are readily discov- 

 ered, especially if they are moving about. As a general 

 rule the wingless flies are found only early in the morning, 

 though in one case a female was discovered crawling over 

 the snow in the evening. As the illustrations show both 

 males and females are entirely wingless and there is no trace 

 left of the wings. The yellov^ halterers, however, are very 

 large and prominent. 



The insects move in a very deliberate wa\' and are ap- 

 parently not afraid of getting cold feet. As a general rule 

 they are observed when the thermometer indicates the freezing 



