The Mother Decides the Sex 



These pear-shaped hollows form splendid 

 lodgings, impregnable strongholds, in which 

 the Osmiae find a safe and commodious re- 

 treat for their families. The Horned Osmia 

 and the Three-horned Osmia establish them- 

 selves there at the same time. Although it 

 is a little too large for her, Latreille's Osmia 

 also appears very well satisfied with it. 



I have examined some forty of the superb 

 cells utilized by each of the first two. The 

 great majority are divided into two storeys by 

 means of a transversal partition. The lower 

 storey includes the larger portion of the An- 

 thophora's cell; the upper storey includes the 

 rest of the cell and a little of the bottle-neck 

 that surmounts it. The two-roomed dwelling 

 is closed, in the passage, by a shapeless, bulky 

 mass of dried mud. What a clumsy artist 

 the Osmia is, compared with the Antho- 

 phora ! Against the exquisite work of the 

 Anthophora, partition and plug strike a note 

 as hideously incongruous as a lump of dirt 

 on polished marble. 



The two apartments thus obtained are of a 

 very unequal capacity, which at once strikes 

 the observer. I measured them with my five- 

 millimetre tube. On an average, the bottom 



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