HYMENOPTERA. — FOSSORES. 187 
has disproved a portion of St. Fargeau’s theory, by observing, that 
although the sand burrowers have spined legs, others which are 
destitute of spines burrow in wood.* (Zrans. Ent. Soc. vol.i.) The 
reason for this appears to me obvious: the sand burrowers have need 
of powerful brushes to enable them to make their way through the 
fine loose particles of sand, whilst the wood burrowers must have 
recourse to their strong, broad, and multidentate mandibles. Mr. 
Shuckard has further objected to the supposed use of the spines of 
the hind legs for carrying the prey, regarding them as applicable to 
the formation of the cells, or for the closing of its mouth; in support 
of which latter opinion he has given an instance in which he had 
captured one of these insects with the hind tibie thickly coated with 
clay. It is to be observed, however, that in those Aculeate Hymenoptera 
whose proceedings have been observed, the materials for closing the 
cells are carried by the jaws. I have also published a memoir still 
further limiting the theory of Messrs. St. Fargeau and Shuckard (in 
the Annales Soc. Ent. de France for 1836), having observed the rare 
British species Miscophus bicolor at Coombe Wood, and a species of 
Pompilus on the Drachenfels, both of which are destitute of spines on 
the fore legs {, in the act of burrowing in the sand; and having further 
noticed a female of Pompilus petiolatus, which has simple fore legs, 
engaged in carrying her prey by the help of her jaws and fore legs, 
and not by the help of the hind legs. Cerceris leta, on the other hand 
(whose proceedings I have described in the Zrans. Ent. Soc. vol. i. 
p- 203.), although furnished with strong posterior tibial denticulations, 
carries its prey with its four fore-legs, the hind legs alone being 
extended. 
* St Fargeau himself appears indeed to have been aware of the limitation ne- 
cessary to be thus imposed on his theory, for in his memoir on Crabro he speaks of the 
presence or absence of spines on the anterior tarsi, indicating that these insects “ tra- 
vaillent dans la terre ou dans la bois.” (Ann. Soe. France, 1834, p. 692.) 
+ The variation in the form of the mandibles is not, however, conclusive as to the 
differences in economy ; for in several of the Crabronide, which are distinctly wood- 
borers, the mandibles, as observed by Mr. Shuckard, “are merely bidentate at their 
apex. May not this disparity arise from the different nature of the wood they are 
instinctively led to form their nests in? for I have always found that the insects with 
this shaped mandible make their cells in subputrescent and soft woods, chiefly de- 
caying willows.” (Essay Foss. Hym. p. 12.) 
+ The theory of St. Fargeau ought moreover to apply sto the solitary wasps, 
Odyneri, &c., which are truly fossorial, as well as to the Fossores; and yet the 
females of Odynerus have simple tarsi, but are not parasites, provisioning their 
own nests. (See my notice of the habits of Odynerus Antilope, Trans. Ent, Soc. 
vol. i. p. 78.) 
