1. _gibbus_, Linnæus, ♂♀. 3-4½ lines. (Plate I. fig. 3 ♂♀). _sphecoides_, Kirby, ♀. _monilicornis_, Kirby, ♂. _picea_, Kirby, ♂. 2. _Geoffroyella_, Kirby, ♂♀. 1-3 lines. _divisa_, Kirby, ♂. 3. _fuscipennis_, Germar, ♂♀. 4½-6 lines.
This genus is named from _σφὴξ_, a wasp, from its apparent resemblance to some of the sand wasps.
They are not uncommon insects, and I have found them abundant in sandy spots sporting in the sunshine upon the bare ground, where they run about with great activity, the females chiefly, the males the while disporting themselves upon any flowers that may be adjacent, and they are especially fond of Ragwort. Their prevalent colours are black and red, the latter occurring only on the abdomen in different degrees of intensity and extension, sometimes occupying the whole of that division of the body, and sometimes limited to a band across it. Much difficulty attaches to the determination of the species from the characters which separate them being extremely obscure, for it is not safe to depend upon the differences of the arrangement of colour upon them, as it varies infinitely; nor can their relative sizes be depended upon as a clue, for in individuals which must be admitted to be of the same species, size takes a wider extent of difference than in almost any of the genera of bees. St. Fargeau, who maintains the parasitism of the genus, accounts for it by saying that in depositing their eggs in the nests of the _Andrenæ_, _Halicti_, and _Dasypoda_, the _Sphecodes_ resorts to the burrows of the species of these genera indifferent to their adaptation to its own size, and thus from the abundance or paucity of food so furnished to its larvæ, does it become a large or a small individual. Westwood says the species are parasitical upon Halictus. Latreille says they are parasites. They are certainly just as destitute of the pollinigerous apparatus as the preceding genus. Mr. Thwaites once thought he had detected a good specific character in the differing lengths of the joints of the antennæ, but I believe he never thoroughly satisfied himself of its being practically available. At all events great difficulty still attaches to their rigid and satisfactory determination. There is an array of entomologists who deny their being parasites. Mr. Kirby says they form their burrows in bare sections of sandbanks exposed to the sun, and nine or ten inches deep, and which they smooth with their tongues. But then, in impeachment of the accuracy of his observation, he further supposes there are three sexes, founding his statement upon what Réaumur remarks of having observed pupæ of three different sizes in the burrows. In the first place, it is not conclusive that these pupæ were those of _Sphecodes_, and secondly we know that this condition of three sexes is found only in the social tribes, wherein the peculiarities of the economy exact a division of offices. Therefore his adoption of this inaccuracy militates against the reception of his other statement. But Smith also states that they are not parasites, and apparently founds his assertion upon direct observation. It still, however, remains a debatable point, from the fact of the destitution of pollinigerous brushes, and thence the character of the food necessary to be stored for the larva. It would be very satisfactory if these apparent inconsistencies could be lucidly explained.