ars, when it is remembered that selection may be applied to
the family, as well as to the individual, and may thus gain the {238}
desired end. Thus, a well-flavoured vegetable is cooked, and the individual
is destroyed; but the horticulturist sows seeds of the same stock, and
confidently expects to get nearly the same variety: breeders of cattle wish
the flesh and fat to be well marbled together; the animal has been
slaughtered, but the breeder goes with confidence to the same family. I
have such faith in the powers of selection, that I do not doubt that a
breed of cattle, always yielding oxen with extraordinarily long horns,
could be slowly formed by carefully watching which individual bulls and
cows, when matched, produced oxen with the longest horns; and yet no one ox
could ever have propagated its kind. Thus I believe it has been with social
insects: a slight modification of structure, or instinct, correlated with
the sterile condition of certain members of the community, has been
advantageous to the community: consequently the fertile males and females
of the same community flourished, and transmitted to their fertile
offspring a tendency to produce sterile members having the same
modification. And I believe that this process has been repeated, until that
prodigious amount of difference between the fertile and sterile females of
the same species has been produced, which we see in many social insects.

But we have not as yet touched on the climax of the difficulty; namely, the
fact that the neuters of several ants differ, not only from the fertile
females and males, but from each other, sometimes to an almost incredible
degree, and are thus divided into two or even three castes. The castes,
moreover, do not generally graduate into each other, but are perfectly well
defined; being as distinct from each other, as are any two species of the
same genus, or rather as any two genera of the same family. Thus in Eciton,
there are working and soldier neuters, with jaws and instincts
extraordinarily {239} different: in Cryptocerus, the workers of one caste
alone carry a wonderful sort of shield on their heads, the use of which is
quite unknown: in the Mexican Myrmecocystus, the workers of one caste never
leave the nest; they are fed by the workers of another caste, and they have
an enormously developed abdomen which secretes a sort of honey, supplying
the place of that excreted by the aphides, or the domestic cattle as they
may