HYMENOPTERA. ACULEATA. 237 



larly if the soil be clayey, it selects a decaying tree, pre- 

 ferring the stump of an old willow. It lays up a store 

 of pollen and honey for the larvae, which, when full 

 grown, spin a tough dark brown cocoon, in which they 

 remain, in the larva state, until the autumn, when the 

 majority change to pupae, and soon arrive at their perfect 

 condition. Many, however, pass the winter in the larva 

 state. In attempting to account for so remarkable a 

 circumstance all must be conjecture, but it is not of 

 unfrequent occurrence. This species also frequently 

 makes its burrows in the mortar of old walls. Osmia 

 leucomelana may be observed availing itself of a most 

 admirable, and almost ready, adaptation for a burrow ; it 

 selects the dead branches of the common bramble ; with 

 little labour the parent Bee removes the pith, usually to 

 the length of from five to six inches ; at the end she 

 deposits the requisite quantity of food, which she closes 

 in with a substance resembling masticated leaves 

 evidently vegetable matter; she usually forms five or six 

 cells in each bramble-stick. The Bee does not extract 

 the whole of the pith, but alternately widens and contracts 

 the diameter of the tube, each contraction marking the 

 end of a cell. The egg is deposited on the food imme- 

 diately before closing up the cell. It is white, oblong, 

 and about the size and shape of a caraway seed ; the 

 larva is hatched in about eight days, and feeds about 

 ten or twelve, when it is full grown ; it then spins a 

 thin silken covering, and remains in an inactive state 

 until the following spring, when it undergoes its 

 transformation, and appears usually in the month of 

 June. 



" Osmia hirta burrows in wood, seldom in any other 

 material. The same habit will be observed in O. senea ; 



