of the Aculeate Hijmenuptera. 55 



spines of tlie posterior tibife (not the calcaria wlaich arm tlie apex of 

 the limb,) assisted it to carry its jirey ; and consequently such as were 

 unfurnished with these auxiliaries were unable to burrow or convey 

 a prey, and must therefore be joarasitic. This theory he has stated 

 in several articles of the tenth volume of the ' Encyclopedie Metho- 

 dique,' in an early number of Guerin's ' Magazin d'Entomologie/ 

 and has made practical use of it in an analysis and subdivision of 

 Latreille's genus Gorytes, in the first Number of the ' Annales de la 

 Societe Entomologique de France.' I was highly gratified when I first 

 heard of this, and considered it a discovery of an analogous value to 

 that made by Mr. Kirby, of the males of the Aculeate Hymenoptera 

 having one joint in the antennae, and one segment in the abdomen, 

 more than the females. But my pleasure was much decreased, upon 

 inspecting my collection, to find that it furnished me with a negative 

 to the general application of the rule. For chance led me to apply 

 it, in the first place, to the genus Crabro, and here I found C. cepha- 

 lotes with simple tarsi, but with the posterior tibiae spinose ; an 

 anomaly that I could not account for at the time, as I have taken it 

 repeatedly with its prey, and watched it while employing its man- 

 dibles in forming a cylindrical cell in decaying trees : thus the ap- 

 plication of St. Fargeau's theory here would treat as a parasite one 

 of the most ferocious and predatory of this tribe. This is precisely 

 the case also with several other species of the same genus. I next 

 took the genera in regular sequence, and found the genus Sapyga 

 simple in both tarsi and tibiae, and this genus, by St. Fargeau's own 

 admission in his remarks upon it in the 'Encyclopedic Methodique,' is 

 certainly predatorial, as he states having captured Sup. punctata 

 with its prey, which it dropt when caught, but which he detected to 

 be a larva. (Note 2.) We may therefore safely treat it as a true 

 Fossor, although from the nature of the material in which it nidifi- 

 cates it would certainly use its mandibles instead of its tarsi, in exca- 

 vating its little cylindrical cells, and we accordingly find that Nature 

 has provided it with the former excessively strong, and the latter 

 very slender and simple. These instances induced me to suspect 

 that I had detected a clue to the probable cause of this aj^jjarent 

 anomaly (Note 3.) ; for, knowing that these insects nidificate in 

 wood, I surmised that their habit was a consequence of their struc- 

 ture, and that therefore the theory must be limited to such as are 

 strictly burrowers in sand or earth ; and which subsequent investi- 

 gation has tended to confirm ; for I have invariably found such as 

 nidificate in wood, deficient in the ciliae of the anterior tarsi, although 

 having the posterior tibiae occasionally spinose, which seems to sup- 

 port St. Fargeau's opinion, that they are used to assist in conveying 



