provided with eyes, and in
_Atta_, _Eciton_ and other genera, four or five forms of workers are
produced, the largest of which, with huge heads and elongate trenchant
mandibles, are known as the "soldier" caste. The development of such
diversely-formed insects as the offspring of the unmodified females
which show none of their peculiarities raises many points of difficulty
for students in heredity. It is thought that the differences are, in
part at least, due to differences in the nature of the food supplied to
larvae, which are apparently all alike. But the ovaries of worker ants
are in some cases sufficiently developed for the production of eggs,
which may give rise parthenogenetically to male, queen or worker
offspring.

_Food._--Different kinds of ants vary greatly in the substances which
they use for food. Honey forms the staple nourishment of many ants, some
of the workers seeking nectar from flowers, working it up into honey
within their stomachs and regurgitating it so as to feed their comrades
within the nest, who, in their turn, pass it on to the grubs. A curious
specialization of certain workers in connexion with the transference of
honey has been demonstrated by H.C. McCook in the American genus
_Myrmecocystus_, and by later observers in Australian and African
species of _Plagiolepis_ and allied genera. The workers in question
remain within the nest, suspended by their feet, and serve as living
honey-pots for the colony, becoming so distended by the supplies of
honey poured into their mouths by their foraging comrades that their
abdomens become sub-globular, the pale intersegmental membrane being
tightly stretched between the widely-separated dark sclerites. The
"nurse" workers in the nest can then draw their supplies from these
"honey-pots." Very many ants live by preying upon various insects, such
as the British "red ants" with well-developed stings (_Myrmica rubra_),
and the notorious "driver ants" of Africa and America, the old-world
species of which belong to _Dorylus_ and allied genera, and the
new-world species to _Eciton_ (fig. 2, _2, 3_). In these ants the
difference between the large, heavy, winged males and females, and the
small, long-legged, active workers, is so great, that various forms of
the same species have been often referred to distinct genera; in
_Eciton_, for example, the female has a single petiolate abdominal
segment, the worker two. The workers of these ants range over the
country