WONDERS OF INSTINCT 207 



which instinctive behavior often exhibits. The 

 solitary wasp called Eumenes amedei attains great 

 excellence alike in the chase and in the craft of 

 building; it is "a Nimrod and a Vitruvius by 

 turns." With minute pebbles and salivated mortar 

 it builds a finely-finished cupola about three- 

 quarters of an inch in height; the outside is covered 

 with glistening grains of quartz or sometimes with 

 tiny snail shells; the orifice at the top is "like the 

 mouth of an amphora, gracefully curved, worthy 

 of a potter's wheel." After the mother wasp has 

 placed an egg in her well-fashioned nest, she adds 

 five to ten small caterpillars, and it is remarkable 

 that the egg in the well-stocked nest develops into 

 a female wasp, while that in the meagerly pro- 

 visioned nest becomes the much smaller male. It 

 may be that the difference in the nutritive supply 

 determines the forthcoming sex, giving a con- 

 stitutional bias to one side or the other, for 

 Fabre was surely off the track in supposing that 

 "the mother knows beforehand the sex of the egg 

 she is about to lay," and has " a clear vision of the 

 invisible." But to return to the nest, after egg- 

 laying and victualing, the next step is to close the 

 orifice with a cement plug, in which there is always 

 set a single tiny pebble. " The ritual never varies." 

 But the touch of perfection is to be found inside, 

 not outside. It appears that the stung caterpillars 

 that form the living larder inside the wasp's cell 

 are but imperfectly paralyzed, and toss about when 

 touched. Now the least pressure would crush the 



