THE MASON BEE. 29 



fly (Diplolepis confluentus), placing them, in this instance eleven 

 in number, in two irregular rows, from which the mature bees 

 issue through a hole in the gall (Fig. 27, with two separate cells). 

 The earthen cells, containing the tough dense cocoons, were 

 arranged irregularly so as to fit the concave vault of the larger 

 gall, which was about two inches in diameter. On emerging 

 from the cell the Osmia cuts out with its powerful jaws an ovate 

 lid, nearly as large as one side of the cell. 



In the Harris collection are the cells and specimens of Osmia 

 pacifica, the peaceful Osmia, which, according to the manuscript 



27. Nest of Osmia in a gall. 



notes of Dr. Harris, is found in tne perfect state in earthen cells 

 beneath stones. The cell is oval cylindrical, a little contracted 

 as usual with those of all the species of the genus, thus forming 

 an urn-shaped cell. It is half an inch long, and nearly three- 

 tenths of an inch wide, while the cocoon, which is rather thin, 

 is three-tenths of an inch long. We are not acquainted with 

 the habits of the larva and pupa in this country, but Mr. F. 

 Smith states that the larva of the English species hatches 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. 



