Bramble-bees and Others 



series, both sexes are usually present; and, if 

 the Mason-bee's chamber is at the end of the 

 passage, it is inhabited by a female Osmia. 



We come back to what the short tubes and 

 the old nests of the Mason-bee of the Pebbles 

 have already taught us. The Osmia who, in 

 tubes of sufficient length, divides her whole 

 laying into a continuous sequence of females 

 and a continuous sequence of males, now 

 breaks it up into short series in which both 

 sexes are present. She adapts her sectional 

 layings to the exigencies of a chance lodging; 

 she always places a female in the sumptuous 

 chamber which the Mason-bee or the Antho- 

 phora occupied originally. 



Facts even more striking are supplied by 

 the old nests of the Masked Anthophora 

 {A. personata, Illig.), old nests which 

 I have seen utilized by the Horned Osmia 

 and the Three-horned Osmia at the same 

 time. Less frequently, the same nests serve 

 for Latreille's Osmia. Let us first describe 

 the Masked Anthophora's nests. 



In a steep bank of sandy clay, we find a set 

 of round, wide-open holes. There are gen- 

 erally only a few of them, each about 

 half an inch in diameter. They are the en- 



144 



