Both works were published in the same year, 1802 (An X. of Latreille’s book), unknown to each other, but Mr. Kirby’s sprang into life in matured perfection, like the imago of the bee itself, whereas Latreille’s labours were progressively nursed to maturity in successive publications, until they received their final elaboration in 1809, in the fourth volume of his ‘Genera Crustaceorum et Insectorum,’ whose successive stages were, first, the notice appended at the end of his ‘Histoire des Fourmis’ in Paris in 1801, and then in the thirteenth volume of his ‘Histoire Naturelle des Insectes,’ in 1805, a supplement to Sonnini’s edition of Buffon, and then in the ‘Nouveau Dictionnaire d’Histoire Naturelle.’ Even thus the subject was not so amply discussed, although applied more extensively, and made to embrace all the bees, exotic as well as European, at that time known, as it had been done in Mr. Kirby’s model work, which leaves nothing to be desired but the naming of his anonymous subdivisions, and a little more artistical skill in the execution of his plates. The terminology used by him also differs from that subsequently adopted through foreign influences, but which is readily reduced to his standard. The merits of the work greatly transcend these trivial deficiencies, for it is a “canon” as invaluable to the entomologist as the celebrated canon of Polycletus was, and the Phidian marbles still are to sculptors. Of course observation has greatly reduced the number of his species by their due association with legitimate partners, which, from their dissimilarity, he was compelled to separate, as only successive observation could prove their identity. More extensive collecting has also shown that some of his species are merely varieties of others, which have thus been brought to their authentic type. This also could only be proved by experience, for it is remarkable how very Protean some species are, whilst others are almost rigidly unchangeable. Evidently there does exist a line of demarcation between distinct species, which only requires to be diligently sought to be found, obscure as it may appear to be, but which the insects themselves obey, for however closely species may sometimes approximate, yet I do not believe, as I have before expressed, that they ever permanently coalesce, and that they are always as distinctly separate as are asymptotes. As Mr. Kirby’s work is in few hands, or perhaps not readily accessible, I will give here a summary outline of it, with the names of the genera with which his families coincide. In this work he established only two named genera—_Melitta_ and _Apis_.