Field Studies of the Non-Social Wasps 449 
The second problem, the position of the egg in the 
nest of 8S. caementarium, and the experiments made to 
test Fabre’s work with the mud-dauber of France, is 
given in the following pages. 
Tue Prey or Sceliphron Caementarium. 
After reading Fabre’s account of the nest-building of 
the French mud-dauber and his experiments in trying 
to mislead its instincts, one is left with a feeling that 
these creatures are bundles of stupidity. This is what 
happens, to quote Fabre’s words :* 
‘*A cell has recently been completed. The huntress 
arrives with the first spider. She stores it away and 
at once fastens her egg upon the spider’s belly. She 
sets out on a second trip. I take advantage of her ab- 
sence to remove with my tweezers from the bottom of 
the cell the head of game and the egg. What will the 
insect do on its return, confronted with the empty cell, 
this cell no longer containing the egg, the sole object of 
her industry as a potter and her skill as a huntress? 
‘‘The disappearance of the egg must be obvious to 
the wasp who has been robbed of it, if her poor intelli- 
gence possesses so much as the rudimentary gleam that 
enables us to distinguish between a thing’s presence and 
its absence. The egg, were it alone, . . . might escape 
the mother’s vigilance; but it lies upon a comparatively 
bulky spider, of whose presence the Pelopoeus,** on re- 
turning to the nest, is undoubtedly apprised of by the 
sense of touch and sight when she deposits the second 
victim beside the first. Once more, what will the Pelo- 
poeus do when confronted with her cell, where the ab- 
*The Mason Wasps, p. 109, 1919. : 
**Fabre uses the generic name Pelopoeus, which is synonymous 
with Sceliphron. 
