SOLITARY BEES AND WASPS OF ESSEX. 83
In these situations separate cells are constructed in which pro-
vision is deposited in the shape of a mixture of honey and pollen
in the case of the bees, and of one or more caterpillars, or other
insects ; or spiders (all paralyzed by suitable stinging) in the case
of the wasps ; such provision is usually just sufficient to enable
the larva which hatches from the egg laid in each cell to attain
maturity. In order to prevent the honey mixture from soaking
into the wall of the burrow some of the species line both burrow
and cell with one or more layers of a secretion which dries into a
sort of membranous skin, whilst one genus lines its cells with
sections cut from the leaves or petals of plants.
The larvae are whitish and grublike, being destitute of limbs
of any kind. When full grown they spin the customary cocoon
in the cell, and in due course change to pupae. This "due
course" is long or short according to the single- or double-
broodedness of the species (i.e., whether one or more generations
are produced in a single year), the larvae of some species resting
in their cocoons from about August to April before becoming
pupae. The pupae are shaped like the perfect insect, but the
legs, wings and antennae are swathed in an exceedingly thin
pellicle and pressed close to the body.
The earliest species to appear frequent the blossoms of the
sallows and other early flowers about February and March ; later
on, fruit trees, sloes, brambles, hawthorns, Potentilla, dandelions,
and other yellow composites, Umbellifera, clover, gorse, mignon-
ette, Veronica cliamaedrys, thistles, wild geraniums and many
other plants prove attractive. These insects fly only in sunshine,
disappearing as if by magic should a cloud cover the sun or a few
drops of rain fall. Their sensitiveness to weather changes is
extremely remarkable, and it is probably not too much to say that
their welfare is more dependent on the weather than that of any
other group of insects. They appear to be able to foresee coming
wet, and then will not stir from their burrows, whilst long spells
of cold rainy weather, or heavy storms, may work terrible havoc
among them, whole colonies having been known to be destroyed
by such inclement weather.
The females of the vegetarian species are mostly provided
with facilities for collecting and carrying pollen and nectar, but
one genus (Hyleeus, formerly Prosopis) has no pollen-carrying
apparatus, the pollen being swept into the mouth by the