Wasps, Bees, and Ants 
555 
find in the combination the springs of most if not all ant behavior; and what 
will explain the complex activities of ants will certainly explain those of all 
the other so-called “intelligent insects,” namely, bees and wasps, both soli¬ 
tary and social. 
A final problem in the life of the social insects is that touching the origin 
and establishment of the various castes or kinds of individuals inside the 
single species. The presence of two, often widely differing kinds of indi¬ 
vidual-, namely, male and female, is so familiar as to lose, for some of us,, 
part of its significance and importance. But why the young produced by 
the union of male and female can differ so widely as they may, that is, to the 
extent of the difference between male and female, seems to us explicable by 
the fact that just such two differing parent individuals take part in the pro¬ 
duction of the new individuals, and by the fact that such a phenomenon 
is the usual and ordinary one of heredity. (However little we may under¬ 
stand the natural phenomenon or law of heredity just as little do we under¬ 
stand gravitation, which we habitually are content to assign as an ultimate 
cause for certain effects). But with the social insects we have always one, 
and often more than one, still different individual among the offspring, and 
one which takes no part whatever in the (embryonic) production of new 
individuals; it can hand on nothing to the offspring by heredity. The ques¬ 
tion is, then, how are two kinds of individuals (male and female) able to 
produce not only their own kinds, but a third kind which has no part in pro¬ 
ducing or fertilizing the egg-cell from which it develops? 
And on the heels of this question comes a second. How is it that if the 
present-day forms and kinds of animals are due to the results of the com¬ 
bined influences of variation, natural selection, and heredity—that is, that 
the inevitably appearing slight congenital differences as they are of advantage 
or disadvantage in the life of the animal are preserved or destroyed in the 
species by natural selection—how, it may be asked, have the characters of 
the worker castes been thus determined by selection, for in this case the 
modified individuals have no part in the transmission of their characteristics, 
by heredity? 
The first question is answered as far as it at present can be in terms not 
wholly agnostic, by the statement that it is probably true among ants, as 
has been shown actually to be true with certain other social insects, namely,, 
the termites (p. in) and the honey-bee (p. 525), that the difference between, 
queen (fertile female) and worker (infertile female) is brought about during 
postembryonal development by differences regulated by the nurses in the 
quality and quantity of food supplied the developing individuals. Sharp 
says: “There is a considerable body of evidence suggesting that the quality 
or quantity of the food or both combined are important factors in the treat- 
