This genus was named by Fabricius from the _Nomades_, a pastoral Scythian tribe, in allusion to the assumed wandering habits of the insects, and it is the fact indeed that they are usually found leisurely hovering about hedge-rows, or the banks enclosing fields, or about the metropolis or nidus of any bee upon which they are parasitical. They are the gayest of all our bees, their colours being red or yellow intermixed with black, in bands or spots; they are also very elegant in form, which is after the type of that of the most normal _Andrenidæ_, and to which they have a further affinity by the silence of their flight, and by their parasitism upon many of the species of that subfamily. From their very general resemblance to wasps in colour they are often mistaken for wasps, and are popularly called wasp-bees, although they have none of the virulence of that vindictive tribe, for although all the females are armed with stings, they are not prompt in their use, or if roused to defence the puncture is but slight. In addition to their prettiness of colour and elegance of form, they have a further attraction in the agreeable odours they emit, sometimes of a balmy or balsamical, and sometimes of a mixed character, and often as sweet as the _pot-pourri_, and occasionally pleasantly pungent. A fine string of specimens of the several species is a great ornament to a collection, but to secure this in its perfection some care is required in the mode of killing them. Their colours are best permanently retained by suffocating them with sulphur, which fixes the reds and yellows in all their natural and living purity. My method was in my collecting excursions to convey with me a large store of pill-boxes of various sizes, and as I captured insects in my green gauze bag-net, I transferred them separately to these boxes. When home again I lifted the lids slightly on one side and placed as many as would readily go beneath a tumbler, and then fumigated them with the sulphur. This is a better plan than killing them with crushed laurel-leaves, for it leaves the limbs much longer flexible for the purposes of setting, whereas the laurel has a tendency to make them rigid, and this rigidity is extremely difficult to relax, whereas the setting of those killed with sulphur, if they are kept in a cool place, may be deferred for a few days, until leisure intervene to permit it, and even then if they become stiffened they are readily relaxed for the purpose.