As a rule the male is rather smaller and especially slenderer than the
female, but there are notable exceptions; in one genus of the fossors,
_Myrmosa_ for instance, the male is many times larger than the female. In
this case the male is winged and the female is wingless. Also, if there is
a difference in brightness of coloration between the sexes, as a rule the
male is duller than the female--this is especially the case among the
bees--but if there is any eccentricity in the form of the limbs it is
almost sure to occur in the male, and I think one would not go far wrong in
saying that when peculiar features occur in the female, the reason for them
is more or less apparent, whereas for the eccentricities of the male there
really often seems to be no assignable cause. These male eccentricities are
often exceedingly marked. A very good {101} [Illustration: FIG. 23.]
[Illustration: FIG. 24.] example of them occurs among the small "keyhole"
wasps. All the British species are practically alike in coloration. They
may vary in having a greater or less number of yellow bands on the body,
but otherwise their distinctions rest on structure. In the females the
antennae are slightly thickened towards the apex, but otherwise they are
simple. The males, however, are divided into three quite distinct groups.
In the first of these, the end joints of the antennae are rolled up in more
or less of a spiral (fig. 23, 2); in the second, the apical joint is turned
sharply back like a hook (fig. 23, 1); in the third, the end joints of the
antennae are simple and more or less like those of the female. Now if we
examine the legs of the males in the first group we shall find still
greater peculiarities; in two of our species there is a long yellow spine
at the extreme base of the middle leg on the little joint by which it
articulates on to the body (fig. 24, 2), and a curious pencil of hairs
{102} on each side of the mouth. In two others, the femora, or thighs of
the middle legs, are cut into two deep somewhat semicircular incisions
(fig. 24, 1)--a most curious character; but here again the females have no
corresponding peculiarities. There seems to be no explanation known for
these vagaries, and yet one feels that there must be some object served by
them. If we turn to the bees we shall find that in many species the face of
the male is white to a greater or less extent, whereas that character is
very rare in the female. The front feet are produced into a wide flattened
form in some, in others the middle legs are extraordinarily developed, and
provided with tufts of hairs, etc. Another form of male development lies in
the form of the head. This is sometimes very much enlarged--often varying
considerably in this respect in specimens of the same species; there is
often a projecting tooth or spine on the mandible or jaw at its base, or
frequently on the cheek just above it. Then in the fossors the males of the
genus _Crabro_ break out into numerous eccentricities; in some, two or more
of the joints of the antennae are soldered together and curved or cut out
into {103} curious forms (fig. 26); in others the front shin or tibia is
formed like a concave shield or shell (fig. 25), and all the joints of that
leg more or less distorted; in another male (a rather doubtful native which
has not been taken in this country for fifty years) the head is narrowed
behind into an almost ridiculously small neck, being quite triangular in
form, viewed from above, with the eyes projecting from its anterior angles
(fig. 27, 1), the female head being of normal form (fig. 27, 2).
[Illustration: FIG. 25.]
[Illustration: FIG. 26.]
[Illustration: FIG. 27.]
In the males of several species of fossors and bees the eyes are enormously
developed, joining one another on the top of the head. This condition
occurs also in the drone of the hive bee. The male of _Astatus_, which has
this character, has also a peculiar habit. It sits basking in the sun on
some bare sandy spot, and when disturbed makes a sort of circular detour
and pitches down again exactly on the spot from which it started up. An
{104} increased length of the antennae is another male characteristic. This
is carried to an extraordinary development in what is called the "long
horned bee"; this bee, which is pretty common in some places, has antennae
which, when directed backwards, are almost as long as its body--the female
has quite an ordinary pair.
Another set of male characters which are of great value to systematists
lies in the hidden apical segments of the underside; although these are
hidden, being telescoped up inside the segments which close the apical
opening of the body, they often assume most curious and beautiful forms,
and are characters whereby the males of a species may be determined with
certainty when the females defy all one's endeavours to discover their
identity.
* * * * *
{105}