84 THE ESSEX NATURALIST.
anterior feet, and afterwards injected with the honey into the
cells. As a contrast to this, another genus (Andrena) carries
its pollen on the whole length of the hind legs, except the feet,
and has on the. trochanters a special tuft of long hairs, called the
"floccus," to provide additional accommodation for it.
The bees have been grouped as Obtusilingues, or "blunt-
tongued," and Acutilingues, or "sharp-tongued," the former
group comprising the primitive families Hylaeidae and Colletidae
only, the other, the higher bees, Andrenidae, Ceratinidae,
Athophoridae, Megachilidae, Bombidae. and Apidae ; the last two
families consist of the Humble-bees and Honey-bees respectively,
which do not come within our present purview. The Fossores,
being neither wasps nor bees, are also omitted.
The wasps consist of the Vespidae (Social) and Eiimcnidae
(Solitary), the last only concerning us here.
The "Cuckoo" bees are characterised by the absence of
pollinigerous organs, since they do not require to collect pollen.
They subsist on nectar and frequent flowers—often the same
flowers—as do their hosts. In flight they are even slower and
quieter than their hosts, although many species of the latter—
notably the Andrenae—are conspicuously silent on the wing. In
large colonies, however, the combined hum of the many inhabi-
tants (hosts and "cuckoos") is sometimes quite audible even at
a little distance. The "cuckoos" in some cases differ much
from their hosts in both appearance and structure ; e.g.,
Sphecodes from Halictus and Nomada horn Andrena ; whilst
others resemble their hosts so closely that differentiation of
them on the wing is by no means easy, e.g. Psithyrus and Bombus.
There are reasons for thinking that in the latter groups at least
the "cuckoos" are degenerates from the same stocks as their
hosts. The female "cuckoo" bees fly slowly about the burrows
of their hosts, into which they creep to lay their eggs on the food
provided for the host larvae, and it is remarkable that they
appear to meet with little, if any, resistance from the owner of the
burrow in the case of the solitary species, females of the latter
arriving at their burrow-entrance, while the cuckoo was inside
at her deadly work, having been commonly observed to wait
meekly outside until the enemy came forth. That their meekness
is not universal is, however, shown by Mr. Mothersole in his
interesting notes on Megachile ligniseca and its "cuckoo,"