THE OSMIA LEUCOMELANA. 
109 
Five or six cells are made in each branch, and the perfect in- 
sect appears about the month of June. 
Several species select localities even more remarkable, and 
make their nests in the empty shells of snails. The common 
banded snail is a favourite with these bees, and in the British 
Museum may be seen a whole series of such nests. The number 
of cells necessarily varies with the size of the snail shell and the 
number of its whorls, but on the average four or five cells are 
found in each snail shell. The process of forming the cells is 
very simple. First, the bee deposits a quantity of pollen and 
honey, then she places an egg upon the pollen, and then she 
makes a partition with vegetable fibres torn by her teeth and 
kneaded firmly together. Lastly, the whole opening of the cell 
is closed by a wall formed of clay, tiny bits of stick, and small 
stones, and then the bee goes off in search of another shell. 
These shells may often be found under hedges, in moss, hidden 
by grass, and on examination the nests of bees will frequently 
be seen in them. 
When the Osmia burrows into wood, she sets to work in a 
very deliberate manner. ‘ A bee/ writes Mr. F. Smith, 4 is ob- 
served to alight on an upright post, or other wood suitable for 
its purposes. She commences the formation of her tunnel, not 
by excavating downwards, as she would be incommoded with 
the dust and rubbish which she removes ; no, she work upwards , 
and so avoids such an inconvenience. When she has proceeded 
to the length required, she proceeds in a horizontal direction to 
the outside of the post, and then her operations are continued 
downwards. She excavates a cell near the bottom of the tube, 
a second and a third, and so on to the required number. The 
larvae when full fed have their heads turned upwards. The 
bees which arrive at their perfect condition, or rather those 
which are first anxious to escape into day, are two or three in 
the upper cells — these are males ; the females are usually ten 
or twelve days later. This is the history of every wood-boring 
bee which I have bred, and I have reared broods of nearly 
every species indigenous to this country/ 
