n] FOSSORES OR DIGGER-WASPS 11 



and departed. On my return I found that the sand- 

 wasp had disdained my proffered assistance and had 

 opened a new hole just below my own unskilled 

 attempt. 



This little accident gives one possible clue to the 

 incessant anxiety exhibited as to the welfare of the 

 burrow. The surface of the sand is so loose that 

 a very slight or even no apparent disturbance will 

 set quantities of it sliding ; so that it must frequently 

 occur that the mouths of the wasps' burrows get 

 smothered. Hence it becomes of prime importance 

 to make sure that the hole remains open when the 

 wasp is actually engaged in laying in supplies for 

 her onspring. The opening up of the fresh hole is 

 probably also a matter of daily occurrence; for at 

 the end of any hot day very few holes are to be seen, 

 and promiscuous digging into sand which had no 

 holes visible frequently resulted in exhuming nu- 

 merous sand- wasps which were buried for the night, 

 and which would be constrained to make for them- 

 selves an exit next morning. Further it is apparently 

 easier to make a clean hole in wind-blown sand by 

 working from within outwards than in the reverse 

 direction; for this species was never observed to 

 succeed in digging a burrow at any of the numer- 

 ous attempts upon the surface: doubtless also the 

 slight coherence possessed by the surface when 

 moist with the morning dew makes the task of 



