The genus NOMADA is the first of the genuine parasitical bees, and about the habits of which no doubt can be entertained; certainly not the same as attaches both to _Hylæus_ and _Sphecodes_, among the _Andrenidæ_. The parasitical habits of Nomada are evident and unmistakable. This is the handsomest genus, in variety of colour and elegance of form, of all our native bees, but the species are never conspicuous for size. They have much of the appearance of wasps, and are often mistaken for them even by entomologists, who have not paid attention to bees. Many of our native species seem limited to our own islands: others of our species occur in France and Germany, and through Denmark in direct line to Lapland, turning down into Russia, and have been caught as far south as Albania. One of our species, or so like as to want distinguishing characteristics, is found in Canada. Did ours migrate there? and how? The genus is of wide distribution, but occurs only north of the Equator, where it spreads from Portugal to the Philippine Islands. It is found in Siberia and Northern China, whence through the Philippines it passes to Tranquebar, then up to Northern India, and thence by Bagdad to the Morea and Albania, and dips down to Northern Africa at Tunis, and on to Oran and Tangiers, and completes its circuit in Portugal. It is doubtless parasitical upon many more genera and species than we find it infest in this country, although all that the several species pair off with here are not fully designated, especially among the _Andrenæ_, and smaller _Halicti_. The number of species, British and foreign, known to collectors approximate to a hundred. The genus MELECTA is another handsome parasitical insect. This is always a dark beauty, and is very limited in species, for, as far as they may be estimated from the contents of collections, its numbers do not reach twenty. Our own species occur throughout the whole of Europe, north and south. Others are found in Sicily, Albania, the Morea, and show themselves at Bagdad. The genus has been sent from the Canaries, and crosses the tropics into Chili, but does not seem to have occurred elsewhere in either North or South America, although one of the genera (_Eucera_) on which, with us, it is parasitical, is found in the latter country, and the other genus (_Anthophora_), which it also infests, is found throughout the world, excepting in Australasia. In all those countries, the closely-allied exotic genus _Crocisa_, which is very numerous in species, may supply its place.