The site of the nest is usually a slight depression in the soil in the
shelter of a cardoon bush. The bees deepen the hollow by burrowing in
the earth; and when the spring foliage sheltering it withers up, they
construct a dome-shaped covering of small sticks, thorns, and leaves
bitten into extremely minute pieces. They sometimes take possession of a
small hole or cavity in the ground, and save themselves the labour of
excavation.

Their architecture closely resembles that of B. terrestris. They make
rudely-shaped oval honey-cells, varying from half an inch to an inch and
a half in length, the smaller ones being the first made; later in the
season the old cocoons are utilized for storing honey. The wax is
chocolate-coloured, and almost the only difference I can find in the
economy of the two species is that the black bee uses a large quantity
of wax in plastering the interior of its nest. The egg-cell of the
yellow bee always contains from twelve to sixteen eggs; that of the
black bee from ten to fourteen; and the eggs of this species are the
largest though the bee is smallest. At the entrance on the edge of the
mound one bee is usually stationed, and, when approached, it hums a
shrill challenge, and throws itself into a menacing attitude. The sting
is exceedingly painful.

One summer I was so fortunate as to discover two nests of the two kinds
within twelve yards of each other, and I resolved to watch them very
carefully, in order to see whether the two species ever came into
collision, as sometimes happens with ants of different species living
close together. Several times I saw a yellow bee leave its own nest and
hover round or settle on the neighbouring one, upon which the sentinel
black bee would attack and drive it off. One day, while watching, I was
delighted to see a yellow bee actually enter its neighbour's nest, the