We are told of the occasional occurrence of hermaphrodite bees, half workers and half drones, and the explanation of their existence is given by Von Berlepsch as an incomplete penetration of the shell of the egg, in the act of fertilising, by the spermatozoa. Yet another order of individuals has been supposed to exist by some, and they have termed them "black bees,"[14] also "drone mothers;" they are not, however, the veritable "fertile workers" named above, but owe their distinction solely to misconception. They are blacker than the rest, and often with fewer and shorter hairs: but the above author, after ascertaining from Leuckart that there was no anatomical difference, proved by experiments that their colour was caused simply by smearing with honey, or else was the effect of stifling or of fright, and that the loss of hairs was owing to nothing more than having crept repeatedly through confined entrance-holes! Similarly Dzierzon: "The black colour is one purely accidental, produced through heating, rubbing against sides, biting, smearing, licking, and the like. As a rule, the glossy black bees are _robbers_ which have been pursuing their trade for some considerable time." [Footnote 14: This term is also sometimes applied to English bees generally in distinction from the Italians.] § XI. THE RATIONALE OF SWARMING. Under this heading we purpose to describe such matters as belong chiefly to the natural history of the bee, thus reserving for its proper position at the beginning of our fifth chapter all which strictly belongs to the subject of "Manipulation," and which it is to the convenience of the inexperienced bee-keeper to find brief and ready to his hand at any moment of emergency. A leisurely digesting of the interesting facts stated in the present section will, however, greatly assist him in the intelligent following of his pursuit.