THE VAGARIES OF COLOUR AND STRUCTURE IN THE SEXES
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
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
increased length of the antennæ 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 antennæ 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.