The Distribution of the Sexes 



We do not often come upon complete series, 

 comprising the whole laying, from the first- 

 born to the youngest. As a rule, we find part 

 of a laying, in which the number of cocoons 

 varies greatly, sometimes falling as low as 

 two, or even one. The mother has not 

 deemed it advisable to confide her whole 

 family to a single bramble-stump; In order 

 to make the exit less toilsome, or else for 

 reasons which escape me, she has left the first 

 home and elected to make a second home, per- 

 haps a third or more. 



We also find series with breaks in them. 

 Sometimes, in cells distributed at random, the 

 egg has not developed and the provisions have 

 remained untouched, but mildewed; some- 

 times, the larva has died before spinning its 

 cocoon, or after spinning it. Lastly, there 

 are parasites, such as the Unarmed Zonitis^ 

 and the Spotted Sapyga,^ who interrupt the 

 series by substituting themselves for the 

 original occupant. All these disturbing factors 

 make it necessary to examine a large number 

 of nests of the Three-pronged Osmia, if we 

 would obtain a definite result, 



^Zonitis mutica, one of the Oil-beetles. — Translator's 

 Note. 



^A Digget-wasp. — Translator's Note. 



93 



