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 
