INTELLIGENT BEHAVIOUR IN INSECTS 129 
she rose higher in the air, until at last she took a straight line 
and disappeared in the distance.” Another species (Cerceris 
deserta) “has the habit of making a number of half circles in 
front of the nest, and then, after rising a little higher, of 
flying several times completely round it.” The method of 
procedure is, it seems, so normal to the species that it is pro- 
bably founded on an instinctive basis. Dr. and Mrs, Peckham, 
in commenting on their observations, say : * “If the examination 
of the objects about the nest makes no impression upon the 
wasp, or if it is not remembered, she ought not to be incon- 
venienced nor thrown off her track when weeds and stones 
are removed and the surface of the ground is smoothed over ; 
but this is just what happens.” For convenience of observa- 
tion they “sometimes gently moved intercepting objects to 
one side, but even such a slight change threw the wasp out 
of her bearings, and made it difficult for her to recover her 
treasure.” Where wasps form a number of nests in a small 
plot of ground, as in the case of Bember, each knows and 
returns to its own hole, as was proved by Dr. Peckham, who 
marked the insects and their nests with paint. 
So, too, with regard to prey. In the course of his observa- 
tions on Pompilus, Fabre removed the spider which the wasp 
had deposited on a tuft of vegetation before she made her 
nest. As she was at work beneath the surface she could not 
see what went on above ground or where the spider had been 
redeposited some twenty inches from its former position. On 
emerging from the nest the wasp went straight to the original 
spot, searched round it for some time, then made further 
excursions, and discovered the spider. After slightly altering 
its position, and placing it on another tuft of vegetation, she 
returned to her subterranean labours, giving the observer an 
opportunity of again moving the spider. Five times did 
Fabre repeat the operation, and every time the wasp returned 
to the spot where she had last deposited her prey. 
The same observer records some interesting experiments 
with the mason bee, Chalicodoma. The mud nests of the species 
* Op. ctt., p. 215. 
K 
