These differ from each other very greatly in many cases. Eccentricity in
structure almost always occurs in the male; excess of coloration usually in
the female. In size the male is generally the smaller and the less robustly
built of the two. Among the pollen-collectors, the male is usually less
densely clothed with hairs than the [female]. In the fossors this rule is
rather reversed, but in that section neither sex is densely clothed with
hairs as are most of the pollenigerous bees.
The male has normally thirteen joints in its antennae, and the female only
twelve. There are exceptions to this rule amongst the ants and in certain
fossors of the genus _Crabro_, some species of which have the antennae
considerably distorted, and have two joints welded apparently into one.
Another distinction between the sexes is that the male has seven dorsal
segments {96} of the body exposed to view, and the female only six. In the
males of some of those bees which collect pollen on the underside of the
body, the body above terminates with the sixth segment. This is because the
seventh is turned over on to the underside, and faces downwards, its apex
pointing towards the head. This arrangement of course leaves less room for
the regular ventral segments, and the usual apical segments are in
consequence "telescoped" up under the fourth, so that the apical opening of
the body lies on its underside between the fourth ventral and the inverted
seventh dorsal segments. This very curious structure occurs only in those
bees whose females collect pollen on the underside, and the reason of it is
to me quite inexplicable. The females of a few of the fossors are destitute
of wings; but in this country we have no wingless males, except in the case
of one little ant (_Formicoxenus_); this lives in the nest of the common
large red ant, and its male can hardly be known from the worker except by
the number of joints in the antennae and the absence of a sting. In the
cases where the female is wingless, the male as a rule is much the larger
of the two sexes. {97} There are few more puzzling questions than those
which arise over these eccentricities of structure; they seem to have no
relation to any habits of the creatures' lives so far as we can judge,
neither can one suggest any useful purpose which they can serve. In some
groups the males of all the species seem built on one regular plan--in
others the males of each species seem to vie with the next as to what
eccentricity of structure in antennae or legs or apex of the body it can
exhibit. In numbers, the males probably considerably exceed the females,
and are far more frequently met with, as they seem to be less particular as
to weather, and not being intent on obtaining food for their offspring they
fly about more casually, and certainly are more in evidence generally.
The great difference in structure, etc., between the males and females
makes the work of pairing the sexes very difficult, especially in those
genera where the males and females appear together only for a few weeks, as
is the case in _Halictus_ and _Sphecodes_. If one visits a locality in the
spring one may catch any number of females of _Halictus_, but no males
appear till the late {98} summer or autumn, and, unless one visits the same
spot again when both sexes are out, it is impossible to associate males and
females. I have at the present moment in my collection several males,
which, being in doubt about myself, I have communicated to continental
authorities, who have returned them to me as possibly the male of so and
so! and we shall have to remain in uncertainty about them till some one
happens to take both sexes together, when the mystery will be solved.
In time of appearance the males always precede the females--in burrows,
such as those of the leaf-cutting bees, etc., it may seem puzzling as to
how this is arranged, as one cell is placed over the other so that those
lower down in the tube cannot pass those higher up. This difficulty is got
over by the arrangement that the first eggs laid by the mother bee are
female and the last male, so that those at the top belong to this latter
sex; these emerge as soon as the warmth of the sun is great enough to
energize them sufficiently to break through their cell covering, when they
emerge and wait for the appearance of their females. The males of {99} some
species of _Andrena_ seem to take great pleasure in flying rapidly up and
down hedgerows, hardly ever settling, and apparently far away from their
females, which are probably pollen collecting in dandelions or some such
flowers in the neighbourhood.
* * * * *
{100}