It is the least pubescent of any of the bees, even less so than those confirmed parasites, the genera Nomada and Stelis, thus further tending to corroborate its apparently parasitical habits, for none of the truly pollinigerous bees are so destitute of hair. The ground-colour of the species is intensely black, variously decorated on the face, thorax, and legs, with markings of different intensities of yellow; but one of our species, the P. variegata, is also gaily marked with red. Indeed exotic species, and especially those of warm climates, are often very gay insects.
They have usually been considered as parasitical insects, from their being unfurnished with the customary apparatus of hair upon the posterior legs, with which pollinigerous insects are generally so amply provided. In contradiction to their parasitism, it is asserted that they have been repeatedly bred from bramble sticks; this circumstance is no proof of the fact of their not being parasitical, for many bees, for instance Ceratina, Heriades, etc., nidificate in bramble sticks, and they may have superseded the nidificating bee by depositing their ova in the nests of the latter; although it certainly is a remarkable circumstance that some one of these bees has never escaped destruction in the several instances in which these have been thus bred. It is also said that their nests contain a semi-liquid honey. The fact of the larva of a wild bee being nurtured upon any other provender than a mixture of pollen and honey, does not elsewhere occur, and it would seem to contradict the function this family is ordained to exercise, by conveying pollen from flower to flower, and which besides, in every other case, constitutes the nutritive aliment of the larva. But then, again, the structure of its tongue, which resembles somewhat that of Colletes in lateral expansion, and with which it would be provided for some analogous purpose, seems to contradict parasitical habits, although St. Fargeau asserts that it is parasitical upon this genus, and if so, although it has not been observed in this country, the analogous structure of the tongue might be perhaps explained.
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.
Subsection b. Linguæ lanceolatæ (with lancet-shaped tongues).
Genus 3. Sphecodes, Latreille.
([Plate I.] fig. 3 ♂♀.)
Melitta ** a, Kirby.