The bees discussed below have been placed by some authors in the Nomadidae, treated by others either as a separate family, the Melectidae, or, more rarely, as a subfamily of the Anthophoridae, the Melectinae. Of these alternatives the latter seems most in accord with our present knowledge of the group. The relationship of the melectine bees with the Nomadidae would appear to be remote since the two groups differ markedly in wing structure. In the Melectinae the anterior wing sculpture is highly differentiated with a broad band of minute papillae along the apical margin and the wing hairs reduced to a very few areas, primarily along the anterior margin (see figs. 1-4). The Nomadidae, however, have retained a more primitive wing structure, with the papillae and hairs more or less evenly distributed. Likewise, the nervellus of the posterior wings of the melectines is very oblique, frequently sinuate or curved, and nearly attains the fork of the cubital vein (fig. 5), but is straight and more or less right-angled in the nomadids. These characters suggest an anthophoroid origin for the melectine bees, possibly a panurgoid origin for the nomadids.