298 
BRITISH BEES. 
place tliem end to end, but where it is more roomy they 
affix them side to side, completely adapting themselves 
to the circumstances of the locality as I shall instance 
below, in the description of the special habits of the 
more conspicuous species. I have elsewhere referred to 
the metallic colouring of many of the species of this 
genus, and amongst them is found the greatest sexual 
disparity of personal appearance, the 0. leucomelana, 
and one or two of the neighbouring species being, per¬ 
haps, the only ones wherein uniformity of appearance 
would unite the partners together. The majority are 
very pubescent insects, and the females of the terminal 
species in the foregoing list are remarkable for a couple 
of inwardly curved horns, springing from the base of the 
clypeus just below the insertion of the antennae, an ap¬ 
pendage usually a male attribute. 
There is very great dissimilarity in the habits of the 
various species, whence no single characteristic will em¬ 
brace them, nor is there anv distinctive feature whereby 
the genus might bear subdivision, either from habits or 
habit, as will be collected from the following cursory 
survey of their special natural history. 
Thus the first species, the 0. leucomelana, named so 
from the white decumbent down which edges the black 
segments of the abdomen, extracts the pith from bram¬ 
ble-sticks, and its cells are formed and closed with a 
composition made of triturated Avood or leaves. The 
cylinders it forms are usually about five inches deep, 
and within this it constructs about the same number of 
cells proportionate to the small size of the insect. These 
are midsummer insects, coming forth in June and July; 
they are very local, but seem to abound in the vicinity 
Bristol, whence Mr. Thwaites formerly sent me speci- 
