84 INSECT BEHAVIOR 



swells like a toy balloon when air is blown into it, until it protrudes 

 two or more millimeters in front of the insect's head, pushing the 

 sand or dirt in front of it as it increases. This is followed by a 

 rapid deflation of the ram, which leaves an indentation into which 

 the fly struggles with great effort. Now the first operation is re- 

 peated, the second indentation made and again the insect wedges it- 

 self into it. Thus, after an hour, if the fly is fortunate, it reaches the 

 surface of the ground, where it rests for a time to recover its strength, 

 before launching into a new and sunlit world once more to search out 

 the vermilion-nut, this time as a nursery for its own offspring. 



