48 



HVMENOPTERA 



thus perishes in the cell. Fahre further states with regard t(i 

 these interesting bees, that no structural differences of the feet 

 or mandibles can be detected between the workers in cotton and 

 the workers in resin ; and he also says that in the case where 

 two cells are constructed in one snail-shell, a male individual is 

 produced from the cell of the greater capacity, and a female from 

 the other. 



Osmia is one of the most important of the genera of bees 

 found in Europe, and is remarkable for the diversity of instinct 

 displayed in the formation of the nests of the various species. 

 As a rule they avail themselves for nidification of hollow 

 places already existing ; choosing excavations in wood, in the 



mortar of walls, and even in 

 sandbanks ; in several cases 

 the same species is found to 

 be able to adapt itself to 

 more than one kind of these 

 very different substances. This 

 variety of habit will render 

 it impossible for us to do 

 justice to this interesting- 

 genus within the space at 

 our disposal, and we must 

 content ourselves with a con- 

 sideration of one or two of the more instructive of the traits 

 of Osmia life. 0. tridentata forms its nest in the stems of 

 brambles, of which it excavates the pith ; its mode of working 

 and some other details of its life have been well depicted by 

 Fabre. The Insect having selected a suitaljle bramble-stalk with 

 a cut extremity, forms a cylindrical burrow in the pith thereof, 

 extending the tunnel as far as will be required to allow the 

 construction of ten or more cells placed one after the other in 

 the axis of the cylinder ; the bee does 2iot at fh'st clear out quite 

 all the pith, but merely forms a tunnel through it, and then 

 commences the construction of the first cell, which is placed at 

 the end of the tunnel that is most remote from the entrance. 

 This cavity is to l)e of oval form, and the Insect therefore cuts 

 away more of the pith so as to make an oval space, but somewhat 

 truncate, as it were, at each end, the plane of truncation at the 

 proximal extremity being of course an orifice. The first cell 



Fig. '11. — Osmia tricornis, ?. Algeria. 



