Economy of Energy- 

 accessible chambers are occupied, the actual 

 building begins with a new stratum of cells 

 upon the former edifice, which becomes more 

 and more massive from year to year. 



The Mason-bee of the Shrubs, with her 

 spherical nests hardly larger than walnuts, 

 puzzled me at first. Does she use the old 

 buildings or does she abandon them for good? 

 To-day perplexity makes way for certainty: 

 she uses them very readily. I have several 

 times surprised her lodging her family in the 

 empty rooms of a nest where she was 

 doubtless born herself. Like her kinswoman 

 of the Pebbles, she returns to the native 

 dwelling and fights for its possession. Also, 

 like the dome-builder, she is an anchorite and 

 prefers to cultivate the lean inheritance alone. 

 Sometimes, however, the nest is of exceptional 

 size and harbours a crowd of occupants, who 

 live in peace, each attending to her business, 

 as in the colossal hives in the sheds. If the 

 colony is at all numerous and the estate de- 

 scends to two or three generations in success- 

 ion, with a fresh layer of masonry each year, 

 the normal walnut-sized nest becomes a ball 

 as large as a man's two fists. I have gathered 

 on a pine-tree a nest of the Mason-bee of the 



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