1903 Fossorial Hymcnoptera 33 



surface of the third thoracic segment, whereas there is no 

 such structure in a Crabro ; and while the eyes of an Ento- 

 mognathus have a covering of fine whitish hairs, those of a 

 Crabro are bald. It is thus a fairly simple matter to recog- 

 nise any member of this genus. In habits they resemble 

 others of the same family, and may often be found searching 

 along sunlit walls for their prey, and not infrequently im- 

 prisoned by the glass of a window-pane. Several species 

 have most remarkable expansions of the tarsal joints of the 

 front pair of legs or of other portions of these appendages. 

 So far as I am aware, the use to which these plate-like 

 structures are put is unknown : it is probable that they are 

 for sexual purposes, inasmuch as they occur only in the 

 males. Similar structures are found in some, but not all, 

 species of leaf-cutting bees, and here, too, they are confined 

 to the males. A very interesting bit of research in bionomics 

 awaits some keen-eyed and patient field naturalist in remov- 

 ing our ignorance on this matter. 



Somewhat nearly allied to the Crabros is the genus, Oxy- 

 belus, just referred to, of which one species, O. uniglumis, is 

 extremely common and equally interesting. The general 

 appearance of the animal might cause it at first sight to be 

 mistaken for a bee of the genus Epeolus, both having a black- 

 and-white checked colouring and being not very different in 

 size. Structurally, however, they differ widely not only in 

 the particulars already mentioned earlier in this article, but 

 also in features readily discernible by the unaided eye ; of 

 these, perhaps the most noticeable is a pair of remarkable 

 wing-like triangular expansions of the hinder part of the 

 thorax of Oxybelus : these structures stand up obliquely from 

 the dorso - lateral surface, and are most characteristic of 

 members of this genus. As to their uses and functions I can 

 offer no information, nor am I aware of any suggestions on 

 the subject. 



Like so many, if not all, of the Fossores, 0. uniglumis pro- 

 vides a store of animal food for her young, but herself 

 feeds upon a vegetable diet. In June and July I often see 

 them in numbers on the flowers of the yellow Stonecrop 

 (Sedum acre aitreum), or basking on the warm sand or bare 

 stones near the plants. Often they will dart up in the air 



vol. 11. — no. 5. c 



