138 HYMENOPTERA. 



hairs, becoming shorter and black on the vertex. The nest, 

 preserved in the Harris collection, now in the Museum of the 

 Boston Society of Natural History, is made of rose-leaves, and 

 is scarcely distinguishable from that of M. centuncularis. 



Osmia, the Mason Bee, is another genus of Carpenter or 

 Upholsterer bees. The species are generally bluish, with 

 greenish reflections, with smooth shiny bodies, and the species 

 are of smaller size than in Megachile. The tongue in this 

 genus is three times as long as the labium, tapering from the 

 base to the acute apex, and clothed with short hair. 



Mr. F. Smith states that the larva of the English species 

 hatch in eight days after the eggs are laid, feeds ten to twelve 

 days, when it becomes full-grown, then spins a thin silken 

 covering, and remains in an inactive state until the following 

 spring, when it completes its transformations. 



The habits of the little Mason-bees are quite varied. They 

 construct their cells in the stems of plants and in rotten posts 

 and trees, or, like Andrena, they burrow in sunny banks. An 

 European species selects snail-shells for its nest, wherein it 

 builds its earthen cells, while other species nidificate under 

 stones. Curtis found two hundred and thirty cocoons of a 

 British species {Osmia paretina) , placed on the under side of 

 a flat stone, of which one-third were empty. Of the remainder, 

 the most appeared between March and June, males appearing 

 first ; thirty-five more bees were developed the following spring. 

 Thus there were three successive broods for three succeeding 

 years, so that these bees lived three years before arriving at 

 maturity. 



Mr. G. R. Waterhouse, in the Transactions of the Entomo- 

 logical Society of London, for 1864 (3d series, vol. 2, p. 121), 

 states that the cells of Osmia leucomelana "are formed of mud, 

 and each cell is built separately. The female bee, having de- 

 posited a small pellet of mud in a sheltered spot between some 

 tufts of grass, immediately commences to excavate a small 

 cavity in its upper surface, scraping the mud away from the 

 centre towards the margin by means of her jaws. A small 

 shallow mud-cup is thus produced. It is rough and uneven on 

 the outer surface, but beautifully smooth on the inner. On 

 witnessing thus much of the work performed, I was struck with 



