THE EMPUSA 39 



pose. Should the threatening storm burst, should the 

 stalk sway in the wind, the sleeper is not troubled by her 

 swinging hammock; at most, she presses her forelegs 

 for a moment against the tossed mast. As soon as equi- 

 librium is restored, the favorite posture, that of the hori- 

 zontal lever, is resumed. Perhaps the mandibles, like the 

 bird's toes, possess the faculty of gripping tighter in pro- 

 portion to the rocking of the wind. 



The Ammophila is not the only one to sleep in this 

 singular position, which is copied by many others 

 Anthidia, 1 Odyneri, 2 Eucerae 3 and mainly by the 

 males. All grip a stalk with their mandibles and sleep 

 with their bodies outstretched and their legs folded back. 

 Some, the stouter species, allow themselves to rest the 

 tip of their arched abdomen against the pole. 



This visit to the dormitory of certain Wasps and Bees 

 does not explain the problem of the Empusa; it sets up 

 another one, no less difficult. It shows us how deficient 

 we are in insight, when it comes to differentiating be- 

 tween fatigue and rest in the cogs of the animal ma- 

 chine. The Ammophila, with the static paradox af- 

 forded by her mandibles; the Empusa, with her claws 

 unwearied by ten months' hanging, - leave the physiolo- 

 gist perplexed and make him wonder what really consti- 

 tutes rest. In absolute fact, there is no rest, apart from 

 that which puts an end to life. The struggle never 

 ceases ; some muscle is always toiling, some nerve strain- 



1 Cotton-bees. Translator's Note. 



2 A genus of Mason-wasps. Translator's Note. 



8 A species of Burrowing-bees. Translator's Note. 



