HOW CAN AN "ACULEATE" BE RECOGNIZED?
This is not an easy question to answer. We cannot make hard and fast definitions which will determine exactly what belongs to this group and what to that; there are always some intermediate forms which present themselves and make our classification unsatisfactory, but, I think, for all purposes of practical observation in the field we may say that if we find a creature with four membranous wings, burrowing in the ground or making a nest in any way, it is an aculeate or stinger. Also, that if we find a hairy-bodied insect with four clear wings collecting pollen or sucking nectar from a flower it is a bee. There are, of course, characters by which the stinging groups can be known almost for certain, but there is no single one which can be given to recognize them by.
They are known by a combination of many, and these are frequently small structural details which do not appeal to the field observer; in fact, which are unappreciable except under magnification. One of the chief difficulties experienced by an observer who is not versed in classification is to avoid being deceived by various flies, which in many cases greatly resemble bees, and especially wasps or the wasp-like fossors. They may mostly be known by their flight, and, when they settle, by their behaviour. A fly is more sudden in its movements—those wasp-like flies, for instance, which poise themselves in the air and appear quite stationary but dart off in a second when approached, betray themselves at once by their alertness. Anthophora and Saropoda poise in the air and dart somewhat after the same fashion, but they never remain poised for long, and do not get away from their position so rapidly. Also, a fly when it settles remains quiet, whereas an aculeate if in a flower sets to work collecting pollen, or if basking in the sun on a leaf rarely rests for many seconds without moving in some way. On a flower, if an insect is seen quietly sitting with its head away from the centre of the
flower, it is almost certain to be a fly. Most of the little bees (Halicti) which visit dandelions and such like "composites" fly in to them with some rapidity, attack them sideways, and move round the "flower", no doubt getting pollen from each floret in succession and with a businesslike action about it all, which is very different from the behaviour of any fly. The flies which really closely resemble bees in their flight are those which lay their eggs in the burrows of various bees and sandwasps. They are really deceptive. Last summer on the sandhills at Southbourne, near Bournemouth, I again and again was deceived by a small fly with a red belt across its body, thinking it was a red-bodied sandwasp. These it really only resembles on the wing. After having been taken in once or twice one felt ashamed of oneself for not recognizing it. The flies also which associate with the humble bees are often coloured very much like them, and could easily be mistaken for small specimens of the bees were it not for their behaviour and wings, which show a dark spot on the upper margin, not existing in the wing of the bee.
MALES AND FEMALES
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 ♀. 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 antennæ, 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 antennæ considerably distorted, and have two joints welded apparently into one. Another distinction between the sexes is that the male has seven dorsal segments
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 antennæ 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.