relate, however, what I have observed on the subject.

When engaged in leaf-cutting, plundering farinha, and other
operations, two classes of workers are always seen (Figs. 1 and
2, page 10). They are not, it is true, very sharply defined in
structure, for individuals of intermediate grades occur. All the
work, however, is done by the individuals which have small heads
(Fig. 1), while those which have enormously large heads, the
worker-majors (Fig. 2), are observed to be simply walking about.
I could never satisfy myself as to the function of these worker-
majors. They are not the soldiers or defenders of the working
portion of the community, like the armed class in the termites,
or white ants, for they never fight. The species has no sting,
and does not display active resistance when interfered with. I
once imagined they exercised a sort of superintendence over the
others; but this function is entirely unnecessary in a community
where all work with a precision and regularity resembling the
subordinate parts of a piece of machinery. I came to the
conclusion, at last, that they have no very precisely defined
function. They cannot, however, be entirely useless to the
community, for the sustenance of an idle class of such bulky
individuals would be too heavy a charge for the species to
sustain. I think they serve, in some sort, as passive instruments
of protection to the real workers. Their enormously large, hard,
and indestructible heads may be of use in protecting them against
the attacks of insectivorous animals. They would be, on this
view, a kind of "pieces de resistance," serving as a foil against
onslaughts made on the main body of workers.

The third order of workers is the most curious of all. If the top