THE SQUIRRELS 311 



it develops a thick layer of fat beneath the skin and retires 

 to the burrow to hibernate. 



Woodchucks are commonly trapped or shot, but the easi- 

 est way to kill them is by means of carbon bisulphide. A 

 little of this volatile liquid is poured upon a tuft of dry moss 

 or other absorbent material which is then rolled into the 

 burrow. The openings are now closed by sods or soil, and 

 the liquid will vaporize into a deadly gas heavier than air. 

 This gas will descend to the lower portions of the burrow 

 to destroy the animals that breathe it. If one is sure the 

 burrow is occupied by a wbodchuck, its destruction is com- 

 paratively certain. 



OBSERVATIONS FOR PUPILS 

 Ground Squirrels or Spermophiles 



I . What kinds of ground squirrels, if any, are found in your locality ? 

 Write a short account of what you know about the most abundant 

 species. Follow this outline : — 



Size and color. 



Burrowing habits. 



Feeding habits. 



Crops injured. 



Natural enemies. 



Remedies, especially those you have seen tried. 



Prairie Dog and Woodchuck 



1. If either of these animals is common in your locality, write a 

 brief account under the headings given above. 



2. Read : — 



American Animals, pages 151-159. The Destruction of Prairie Dogs, U. S. 

 Biological Survey, Circular 32. 



