The genus APATHUS, which is parasitical upon _Bombus_, and to the uninitiated has all the appearance of this genus, seems to be the only instance of a parasitical genus of bees so closely resembling the _οἶτος_, (as we may, perhaps, for the sake of avoiding a periphrasis, be allowed to call the bee upon which the parasite is found,) as to be so easily liable to be mistaken for it, and which was indeed the case by even such a sagacious entomologist as the distinguished Latreille; but Kirby had already noticed the difference, suggesting its separation from _Bombus_, until about the time that St. Fargeau was induced to propose a distribution of the Hymenoptera, based generally upon economy and habits, to which he had been led by a refining investigation of structure, that the distinguishing difference was appreciated, and used generically, by Mr. Newman. This difference, like many other simple facts, now that it has been found, is very obvious. It consists in the genus having no neuters, and the female of the species no polliniferous organs, but the determination of the legitimate males, by means other than empirical, is still difficult. In our own species this genus ranges throughout northern Europe, as high as Lapland; a cause for which we shall discover when we trace the geography of the next genus, _Bombus_. One species different from any of ours occurs in the Brazils, and others are found in the Polish Ukraine, and in the United States of North America. The genus appears extremely limited in numbers, for although nearly a hundred of the genus _Bombus_ are known, _Apathus_, in collections, seems limited to ten. This may perhaps arise from want of due observation or from the neglect of their careful separation from that genus, but our own species are far from co-extensive with our native species of _Bombus_.