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.