86
THE ESSEX NATURALIST.
which they swarm ; when the bee visits the next flower some of
these larvae are left on it and attach themselves to the next bee
visiting that flower. In this way they are carried to fresh nests,
and there they penetrate into the larvae of their hosts, in which
they live and pupate. The perfect female Stylops remains in
the bee's body with her head protruding, usually between the
4th and 5th segments, but the male emerges in May or June,
and flies with a remarkably undulating and rapid flight over
the herbage, and sometimes at a great height above the ground,
searching for a bee containing a female. Usually only one
Stylops is found in a bee, but two are not uncommon, and every
number up to five has been recorded. The effect on the bee
varies with its species, size, or sex, and the number of Stylops
carried. When there are several Stylops the abdomen of the
bee is generally much inflated and more or less distorted, and
the unfortunate victim may be able to fly only with difficulty
or not at all. The colours of the bee may be affected, and in
females the pollen-bearing apparatus of the hind legs is always
more or less degenerate. A very noticeable result of stylopi-
sation is that owing to the destruction of the reproductive organs
of the bee the sexes tend to a closer external resemblance,
although the differentiation between them in their normal
state is evident enough.
About 230 species of solitary bees and wasps—bees 212,
wasps 18—have been recorded for the British Isles, and of these
some 140 have been found in Essex, comprising 62 per cent. of
the bees and 78 per cent. of the wasps. These percentages are
interesting when one realises that Essex is essentially a clayey
county, and most of these solitary wasps use clay for their nests,
whilst the bees on the whole prefer the lighter soils, wherever
these are to be found.
Let us now take the groups in order, beginning with the
lowest bees and finishing with the wasps. Brief notes of the
habits of each genus (so far as they are known) precede the
enumeration of the species, which includes the records in the
Victoria County History.
The Colchester district records were compiled by the late
W. H. Harwood and his two sons (neither of whom now resides in
the county), the "district" being practically that part of Essex