The Behavior of the Honey Bee in Pollen Collection

by Dana Brackenridge Casteel

Although the process is a rather delicate one, it is entirely possible so to manipulate the hind legs of a recently killed bee that the corbiculæ of the two legs receive loads of pollen in a manner similar to that above described. To accomplish this successfully the operator must keep the combs of the plantæ well supplied with moistened pollen. If the foot of first one leg and then the other is grasped with forceps and so guided that the pollen combs of one leg rasp over the pecten spines of the other, the pollen from the combs will be transferred to the corbiculæ. To continue the loading process in a proper manner, it is also necessary to flex the planta of each leg just after the pollen combs of the opposite leg have deposited pollen behind the pecten. By this action the auricle is raised, compressing the pollen which the pecten has secured, and forcing some upward into the corbicula. Bees' legs which have been loaded in this artificial manner show pollen masses in their corbiculæ which are entirely similar in appearance to those formed by the labors of the living bee. Moreover, by the above method of manipulation the pollen appears first at the bottom of the basket, along its lower margin, gradually extends upward along the floor of the chamber, comes in contact with the overhanging hairs, and is shaped by them in a natural manner. All attempts to load the baskets by other movements, such as crossing the hind legs and scraping the plantar combs over the lateral edges of the baskets, give results which are entirely different from those achieved by the living bee.

POLLEN MOISTENING.

Many descriptions have been written by others of the method by which pollen is gathered and moistened. Some of these are indefinite, some are incorrect, while others are, in part, at least, similar to my own interpretation of this process. A few citations will here be given:

The bee first strokes the head and the proboscis with the brushes of the forelegs and moistens these brushes with a little honey from the proboscis, so that with later strokes all of the pollen from the head is collected upon these brushes. Then the middle-leg brushes remove this honey-moistened pollen from the forelegs and they also collect pollen from the breast and the sides of the thorax.—[Translation from Alefeld, 1861.]

In his account of the basket-loading process Alefeld assigns to the middle-leg brushes the function of assembling all of the pollen, even that from the plantar combs, and of placing it on the corbiculæ, this latter act being accomplished by combing over the hairy edge of each basket with the middle-leg brush of the same side.

It appears probable that the bee removes the pollen from the head, breast, and abdomen by means of the hairy brushes which are located upon the medial sides of the tarsal segments of all of the legs, being most pronounced upon the hind legs. The pollen is thus brought together and is carried forward to the mouth, where it is moistened with saliva and a little honey.—[Translation from Franz, 1906.]

Franz then says that this moistened pollen is passed backward and loaded.

Since the pollen of many plants is sticky and moist it adheres to the surface of the basket. Dry pollen is moistened by saliva, so that it also sticks,—[Translation from Fleischmann and Zander. 1910.]

Pollen is taken from flowers principally by means of the tongue, but at times, also, by the mandibles, by the forelegs, and middle legs. The brushes of the hind legs also load themselves, collecting from the hairs of the body. The pollen dust thus gathered is always transmitted to the mouth, where it is mixed with saliva.—[Translation from Hommell, 1906.]

Sladen considers the question of how pollen is moistened by the honey bee, humblebee (bumblebee), and some other bees, but does not appear to reach definite conclusions. In one of his papers (1912, c) he states that the pollen of some plants may be found in the mouth cavity and in the region of the mouth, but he reaches the conclusion that this pollen is comparatively "dry," using the word in a "relative sense." He asserts that "nowhere but on the corbicula and hind metatarsal brushes did I find the sticky pollen, except sometimes on the tips of the long, branched hairs on the back (upper) edges of the tibiæ and femora of the middle legs, and then only in heavily laden bees, where it is reasonable to suppose it had collected accidentally as the result of contact with the hind metatarsal brushes."