Feathers and Feelers 153 



The nature of the ground indicates at once why a more 

 complex burrow is unnecessary. In this instance the 

 sand is always moist and more or less closely packed; 

 therefore, its tendency to be blown about is reduced to 

 a minimum. But what of the water? Although the 

 grub need not provide against the hazards of the wind, 

 it is clear that it must guard itself against the silting 

 action of the waves. If we linger here long enough, 

 the animal will show us how^ it overcomes this little 

 difficulty. Still, as a considerable portion of our time 

 has already been consumed in following its present be- 

 havior, it may be well to anticipate by explaining that 

 it plugs up the entrance with sand just before the tide 

 comes in. How it becomes aware of the time for ap- 

 proaching high water is a mystery. Yet this perform- 

 ance is as periodic as the flood. Within the space of 

 an hour or more preceding every rise, it seals its hole 

 as regularly as though it watched a tidal clock. 



The question here arises as to how the larva over- 

 comes being drowned in its narrow cell. This is an- 

 swered in our examination of the burrow itself. As we 

 dig into the porous sand, a noticeable difference is ap- 

 parent in the texture of that portion forming the wall. 

 Instead of falling aw^ay loosely like the neighboring 

 material, the grains that surround the shaft come apart 

 in clumps. This means that they are bound together 

 with a sort of cement. Closer inspection with a glass 

 does, in fact, show this to be the case; furthermore, the 

 adhering particles are fixed in a way that makes the 

 burrow practically water-tight, but admitting the pene- 

 tration of air; the latter feature being of a decided ad- 

 vantage to the animal in its long winter sleep. It is 



