it there. Under the influence of this
weight flexion was produced, but only at the end. This could not
satisfy the insect; it became a question of decreasing the resistance
at the base. The ant gnawed a little at this spot; the desired result
was attained, and the whole length of the leaf became bent over the
building in course of construction. To prevent it bending back, and to
ensure its remaining adherent to the roof, the worker returned to the
plant and placed earth between the sheath and the stalk. This time all
difficulties were surmounted, and there was a solid scaffolding to
support the materials for the roof.

[106] Ebrard, _Etudes de Moeurs_, Geneve, 1864, p. 3.

Among the _Lasius niger_ the independence of the workers is perhaps
still greater; no doubt they do their best to concert their efforts,
but they do not succeed so well as if an inevitable instinct impelled
them. Notwithstanding the irregularities of the construction, it is
possible to recognise in it a whole formed of hollowed, concentric
half-spheres; they have been added one after the other to the surface
to increase the dwelling. The interval between these clay spheres
constitutes a storey, cut up by the partitions which divide it into
chambers and communicating galleries; the roofs of the largest halls
are supported by numerous pillars. (Fig. 40.)

[Illustration: FIG. 40.]

These ants, as Huber has shown, are highly accomplished in the art of
constructing a cupola. When they wish to increase their nest by a new
layer, they take advantage of the first wet day, the rain serving to
agglutinate and unite the materials. They operate in almost the same
way as the _Formica fusca_, though exhibiting more skill and resource
as architects; they know better how to calculate beforehand the number
of pillars required in a hall of a determined size. As soon as the
rain has given the signal for work, they spread themselves abroad and
prepare a very thick terrace on the external surface of the dwelling
which has become too small. They carry to it small balls of earth
ground very fine by their jaws, and then lightly piled up so as to
pulverise afresh; these are then spread over the construction with the
anterior legs. Then, by hollowing out, the ants trace the plan of the
new storey, leaving the walls, partitions, and columns in relief.
After having raised these parts to a sufficient height, all work
together to cover them with a general ceiling, each ant a