PITH-BORING BEES. 179 



ties. Very many species of pith-boring insects are known, most 

 of them inhabiting the dry twigs of the bramble and garden rose. 

 If at the cut end of a branch a round hole be found in the pith, 

 the observer may be sure that a nest of some kind is within. 

 Generally, on carefully laying the branch open, there appears a 

 whole series of cells, one above the other, and in such a case, 

 the cells which are farthest from the aperture always contain 

 the larvEe of female insects, those nearest the entrance being the 

 males. 



Sometimes the nests which are found in the bramble contain 

 the larvae of Osmia leucomelana, a pretty little bee, scarcely more 

 than a quarter of an inch in length, black in colour, with a very 

 glossy abdomen, and a white, downy look about the legs. Five 

 or six cells are made in each branch, and the perfect insect 

 appears about the month of June. 



Other bees of this genus are extremely clever in saving them- 

 selves labour. Although they can dig industriously when obliged 

 to do so, they will never exert this power without compulsion. 

 The smaller species are very fond of making their cells inside 

 straws, and a thatched roof often contains thousands of nests, 

 which are unsuspected by man, and only discovered by the 

 tomtits and other birds, whose sharp eyes soon detect the hidden 

 insect, and whose ready bills pull the straws out of the thatch, 

 and pick the larvae from their cells. Nail-holes in garden walls 

 are often filled with cells, and so are the auger-holes in old rails 

 and posts, from which the wooden pins have fallen. 



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 



n2 



