roduced by the insect in working. These grains of sand glued
together form, on drying, a very resistant wall.[101]

[101] Latreille, "Observations sur l'abeille parietine
(_Anthophora parietina_)," _Annales du Museum d'Hist.
Nat._, t. iii., 1804, p. 257.

The other animals of which I have to speak are genuine masons, who
prepare their mortar by tempering moistened earth. Every one has seen
the Swallow in spring working at its nest in the corner of a window.
It usually establishes its dwelling in an angle, so that the three
existing walls can be utilised, and to have an enclosed space there is
need only to add the face. It usually gives to this the form of a
quarter of a sphere, and begins it by applying earth more or less
mixed with chopped hay against the walls which are to support the
edifice. At the summit of the construction a hole is left for entry
and exit. During the whole of its sojourn in our country the Swallow
uses this dwelling, and even returns to it for many years in
succession, as long as its work will support the attacks of time. The
faithful return of these birds to their old nest has been many times
proved by attaching ribbons to their claws; they have always returned
with the distinctive mark.

[Illustration: FIG. 36.]

The _Chalicodoma_, whose name of Mason Bee indicates the industry it
exercises, is a hymenopterous relative to our Bees, long since
carefully studied by Reaumur. It does not live in societies like the
latter, and exhibits individual initiative and skill as great as the
swallows. The females accomplish the work which I am about to
describe. The little cells which they build are arranged, to the
number of eight or ten together, in the most various places; sometimes
on a pebble, sometimes on a branch, or, again, on a stone wall. (Fig.
36.) The insect collects earth as fine as possible, such as the dust
of a trodden path, and tempers it with its own saliva. It places side
by side these little balls of mortar and the work soon takes the form
of a cupola, to the edge of which it constantly adds new deposits. The
sun quickly dries the hole and gives it the necessary consistence.
When the cell has acquired sufficient height, the _Chalicodoma_
abandons its occupation of mason, and visits flowers for pollen and
nectar wherewith to fill the little chamber. It goes back to the nest,
disgorges its supply, and returns to the field, until the little cup
of earth is full to the