Insects. 1567 



This Bombus is extremely variable in its colouring : to describe all 

 the varieties were supererogatory : those described are the most highly 

 coloured specimens ; others occur in which the yellow colouring be- 

 comes gradually more and more obsolete, until nearly black, there be- 

 ing only a few pale hairs at the tip of the abdomen ; the extreme va- 

 riety occurring most frequently in the female. Still specimens of 

 the other sexes are sometimes found equally dark. 



This bee is very liable to be confounded with the B. hortorum 

 and also with B. soroensis ; but the former bee has a much more an- 

 gular and pointed abdomen, and I have never known either of its 

 sexes to vary in their colouring : the pubescence of B. flavo-nigres- 

 cens is also much coarser than in either of the above species. The 

 female of B. Soroensis has also usually a faint whitish line of hairs on 

 the margins of the second and third segments. The male of this spe- 

 cies may always be distinguished by the colour of the hair on 

 the mandibles, which is ferruginous, in B. hortorum it is black ; 

 and the latter has not the tinge of yellow intermixed with the white at 

 the tip of the abdomen, as in the male of flavo-nigrescens ; from the 

 male of Soroensis it is abundantly distinct. 



I am indebted to Mr. Thwaites, of Bristol, for suggesting the very 

 appropriate name of this bee. Mr. Thwaites was also the first to dis- 

 tinguish this Bombus as a distinct species : it is abundant in the 

 neighbourhood of Bristol, from whence I have received a fine series 

 from Mr. Walcott, an indefatigable investigator of British Hymenop- 

 tera : it also occurs about London, but not very abundantly. 



Osmia pilicornis, Smith. 



Female. — (Length 5 lines). Black ; a few scattered black hairs on 

 the face and cheeks. Antennae slightly piceous beneath. Thorax 

 with a rufo-fulvous pubescence above. Wings slightly fuscous, their 

 apical margins darkest. Abdomen short, and its apical segment acute, 

 the first segment thinly clothed with rufo-fulvous pubescence, beneath, 

 densely clothed with black hair. 



Male. — (Length 4| — 5£ lines). Nigro-aeneous, finely punctured. 

 Antennae as long as the head and thorax, having a thin fringe of hairs 

 beneath ; the face andcheeks clothed with white pubescence, the ver- 

 tex with pale ochraceous, and also the thorax above ; the anterior 

 femora fringed beneath with white ; the posterior femora and tibiae in- 

 crassate, all the tarsi ferruginous beneath. The abdomen has a 

 scattered pale yellow pubescence, becoming pale fulvous at the apex, 

 the sixth and seventh segments are deeply emarginate. 



