But notwithstanding this deficiency of positive characters, from the absence of pollinigerous organs, nature is not to be controlled by laws framed by us upon the imperfect induction of incomplete facts, for if it be incontestable that this genus is constructive and not parasitical, the riddle presented by this structure of its tongue is at once solved, for without any affinity beyond that single peculiarity with _Colletes_, it presents an anomaly of organization which cannot be accounted for but by its application to a use similar to what we find it applied in that extraordinary genus,—a use that could not be extant in a parasite. In _Colletes_ it is the concomitant of as ample a power of collecting pollen as any that we find exhibited throughout the whole range of our native bees, but in _Prosopis_ it is concurrent with a total deficiency of the ordinary apparatus employed for that purpose.
One of the species of this genus has been found near Bristol, with the indication of a _Stylops_ having escaped from it, which is a further extension of the parasitism of that most extraordinary genus, but the _Stylops_ frequenting it has not yet been discovered, which would doubtless present a new species, therefore an interesting addition to the series already known.
These insects are not at all uncommon in some of the species during the latter spring and summer months, and they frequent the several _Resedas_, being very fond of Mignonette. They are also found upon the _Dracocephalum Moldavica_, and occur not unfrequently upon the Onion, which in blossom is the resort of many interesting insects. The majority of them emit when captured, and if held within the fingers, a very pungent citron odour, exceedingly refreshing on a hot day, in intense sunshine. Some of the species are rare, especially those very highly coloured, as is also the _P. dilatata_, so named from the peculiar triangular expansion of the basal joint of the antennæ, the female of which is not known or possibly has only been overlooked or not identified. The _P. varipes_ and _P. variegata_, which are the most richly coloured, occur in the west of England, and in one, the _P. cornuta_, the clypeus is furnished with a tubercle.