The Mason-bees 



each other. The female is of a splendid vel- 

 vety black, with dark-violet wings. In the 

 male, the black velvet is replaced by a rather 

 bright brick-red fleece. The second species, 

 which is much smaller, does not show this 

 contrast of colour: the two sexes wear the 

 same costume, a general mixture of brown, 

 red and grey, while the tips of the wings, 

 washed with violet on a bronzed ground, re- 

 call, but only faintly, the rich purple of the 

 former species. Both begin their labours at 

 the same period, in the early part of May. 



As Reaumur tells us, the Chalicodoma of 

 the Walls in the northern provinces selects a 

 wall directly facing the sun and one not cov- 

 ered with plaster, which might come off and 

 imperil the future of the ceils. She confides 

 her buildings only to solid foundations, such 

 as bare stone. I find her equally prudent in 

 the south; but, for some reason which I do 

 not know, she here generally prefers some 

 other base to the stone of a wall. A rounded 

 pebble, often hardly larger than one's fist, 

 one of those cobbles with which the waters of 

 the glacial period covered the terraces of the 

 Rhone Valley, forms the most popular sup- 

 port. The extreme abundance of these sites 



12 



