132 THE EVOLUTION OF INSTINCT 
untouched, and no malaxation was practised. In the 
second seven stings again, but given in the anterior and 
middle segments, followed by slight malaxation. In the 
third only one sting was given, but the malaxation was 
prolonged and severe.” The severity of the stinging as 
indicated by the conditions of the caterpillars stored in the 
nest also varies. Of fifteen caterpillars which were stung 
by Ammophila urnaria the Peckhams found that “some of 
them lived only three days, others a little longer, while 
still others showed signs of life at the end of two weeks.” 
And in summing up their observations on the stinging in- 
stinct these writers state that “out of forty-five species of 
our solitary wasps about one-third kill their prey outright. 
Of those that remain there is not a single species in which 
the sting is given with invariable accuracy. To judge from 
results they scarcely sting twice alike, since the victims of 
the same wasp may be killed at once or may live from one 
day to six weeks, or perhaps ultimately recover. Even the 
caterpillars of Ammophila, the most distinguished surgeon, 
live anywhere from two to forty days.” 
Contrary to the conclusions of Fabre, who contended that 
the instincts of Ammophila are practically undeviating, the 
Peckhams remark that “the one preéminent, unmistakable 
and ever present fact is variability. Variability in every 
particular—in the shape of the nest and the manner of dig- 
ging it, in the condition of the nest (whether closed or open) 
when left temporarily, in the method of stinging the prey, 
in the degree of malaxation, in the manner of carrying the 
victim, in the way of closing the nest, and last, and most 
important of all, in the condition produced in the victims by 
stinging.” 
Among certain species of ants, Polyergus rufescens and 
several species of Formica and Lasius, whose larve ordinarily 
