646 Reflexes, Instincts, and Intelligence 



"Second experiment. The Sphex is busy closing her burrow where the 

 prey is stored and the egg laid. With her fore tarsi she sweeps backward 

 before her door, and launches from the entrance a spurt of dust, which 

 passes beneath her, and springs up behind in a parabolic curve as continuous 

 as if it were a slender stream of some liquid, so rapidly does she sweep. 

 From time to time she chooses some sand grains with her mandibles, 

 strengthening materials inserted singly in the dusty mass. To consolidate 

 this she beats it with her head, and heaps it with her mandibles. Walled 

 up by this masonry, the entrance rapidly disappears. In the midst of the 

 work I intervene. Having put the Sphex aside I clear out the short gallery 

 carefully with the blade of a knife, take away the materials which block it, 

 and entirely restore the communication of the cell with the outer air. Then, 

 without injuring the edifice, I draw the ephippiger out of the cell where it is 

 lying with its head to the far end, and its ovipositor to the entrance. The 

 egg is as usual on its breast, near the base of one of the hind legs a proof 

 that the Sphex had given her last touch to the burrow, and would never 

 return. These dispositions made and the ephippiger placed safely in a box, 

 I gave up my place to the Sphex, who had been watching while her domi- 

 cile was rifled. Finding the entrance open, she entered and remained some 

 moments, then came forth and took up her work where I interrupted it, 

 beginning to stop the entrance conscientiously, sweeping the dust backward, 

 and transporting sand grains to build them with minute care, as if doing a 

 useful work. The orifice being again thoroughly blocked, she brushed her- 

 self, seemed to give a glance of satisfaction at her work, and finally flew off. 



"Yet she must have known that the burrow was empty, since she had 

 gone inside, and made prolonged stay, but yet after this visit to the plun- 

 dered dwelling, she set to work to close it with as much care as if nothing 

 had happened. Did she propose to turn it later to account, returning with 

 a fresh prey, laying a new egg? In that case the burrow was closed to 

 defend it from indiscreet visitors while the Sphex was away. Or it was a 

 measure of prudence against other miners who might covet a ready-made 

 chamber, or a wise precaution against internal wear and tear, and, in fact, 

 some predatory Hymenoptera are careful when obliged to suspend work to 

 defend the mouth of their burrow by closing it up temporarily. I have seen 

 certain Ammophilae, whose burrow is a vertical well, close the entrance with 

 a little flat stone when the insect goes a-hunting, or stops mining when the 

 hour to leave off work comes at sunset. But in that case the stoppage is 

 slight a mere slab set on the top of the well. It takes but a moment when 

 the insect comes to displace the little flat stone, and the door is open. But 

 what we have just seen the Sphex construct is a solid barrier strong masonry, 

 where layers of alternate dust and gravel occupy the whole passage. It is 

 definitive, and no temporary work, as is sufficiently shown by the careful 



