150 
WILD BEES. 
July, 1889. 
clay in a cavity between tlie stones or bricks of a wall; it 
may be seen building in this manner in the Botanical Gardens, 
any fine day in spring or early summer. 
Another species 0. pilicornis which is a scarce bee, very 
partial to the flowers of the Purple Bugle, 1 have found making 
its nest in hard stony ground, but also in a detached piece of 
dead wood lying on the surface of the soil. 0. parietina 
which frequents hilly or mountainous districts in the more 
Northern counties, seeks out a stone which encloses a cavitv 
beneath it, and attaches its cells to the under surface of this. 
The two species 0. fulviventris and aenea generally burrow in 
posts or rails, but are always willing to make use of the holes 
which have been made by nails in the mortar of walls. The 
former bee I have often watched cutting roughly oval pieces 
from the leaves of rose trees, selecting not the green ones, 
but those which are yellow and decaved : it leaves a ragged 
outline very different from the neat work of the leaf cutting 
bees : and I believe it does not use nieces of leaf of anv 
size, but bites them up to form a kind of cement, with which 
it separates the adjoining cells. 
It cannot be doubted that the exquisite leaf-building of 
the true leaf-cutters (.Megachile) arose from some simple habit 
like this, and we can well imagine the next step to have been 
the employment of the oval piece entire, as a separation 
between the cells—a saving both of time and labour—and 
finally the employment of leaf for all parts of the nidus. 
Two other species, Osmici aurulenta and 0. bicolor , will 
burrow in the ground when the soil is suitable, but they often 
save themselves this labour by making use of empty snail 
shells, in which they construct their cells, separating them by 
transverse partitions and finally closing the opening of the 
shell. But the latter species (0. bicolor) is not content with 
this security, for although the snail shells chosen are 
generally already well concealed by their position, it uses 
other means to render that concealment more perfect. Where 
this bee is plentiful,—and it is usually abundant where it is 
found at all—you may often catch specimens carrying in 
their mandibles pieces of dry grass-stalks of considerable 
length. Grasping these at the middle, they fly off with them 
to their nidus, and arrange them over the shell somewhat in 
the shape of a dome. The labour of the bee in cutting the 
number required and bringing them home—often from a 
considerable distance—must be very great. I have lately 
heard from Mr. Harwood that he has detected another 
species, O. spinulosa, making its nest in snail shells. I Lave 
not found the nidus of this species myself. 
