198 
Psyche 
[December 
to the species, we must agree that its adaptation is very defective. 
It would be better that the mother, less impetuous, would not 
leave the cell for an instant and would not engage in a fight with 
the agressors. Not a single egg would be lost, and the covetous- 
ness of the evil-intentioned ones would not be satisfied. How 
are we to unravel this chaos? I give it up, as far as I am con- 
cerned. We delude ourselves, I believe, in wishing to seek per- 
fection everywhere in nature, and under all conditions. Let us 
recognize that all is not for the best in the realm of the bumble- 
bees anymore than in other realms.” 
Twenty-three years after the publication of this rather 
pessimistic speculation of Perez (1889), another explanation 
was suggested by the late F. W. L. Sladen (1912). 
After having given a detailed description of this strange 
habit of bumblebees in the first part (pp. 51-52) of his admirable 
treatise on bumblebees, Sladen (p. 257) says: think that the 
strange race-suicidal habit the lapidarius workers have of at- 
tempting to devour their mother’s new-laid eggs is associated 
with the parasitism of Psithyrus. It is natural to suppose that 
workers that attempt to devour the eggs of their Psithyrus 
step-mother perpetua^te their egg-devouring instinct through 
their sons that they sometimes succeed in rearing. In support 
of this view it is interesting to note that in nests of B. latreillellus , 
a species that is not preyed upon by any species of Psithyrus, I 
have never seen the queen’s eggs molested by the workers.” 
As I have already pointed out elsewhere (1922a, p. 28), this 
explanation does not seem very plausible. It is a well-known 
fact that ants, even those belonging to species which are not 
molested by parasitic ants, frequently eat their own eggs (cf. 
Wheeler, 1910, p. 332). Moreover, I have frequently seen the 
workers of Bremus fervidus eat their mothers’ eggs, and this 
species (cf. Plath, 1922b) probably does not suffer any species of 
Psithyrus to breed in its nests, a view which is supported by a 
large number of records (10 by Putnam (1864), “a large number” 
by Franklin (1912-13), and 33 by the writer) of fervidus nests, 
none of which were victimized by a Psithyrus. 
In the same year in which Sladen (1912) published his 
work, another explanation was offered by the Danish biologist 
