342 THE WONDER OF LIFE 



against attack : Andrena, Anthophora, Chalico- 

 doma, Osmia, etc. 



3. Females, or females and males, hibernate in com- 



panies : Halictus mono, Xylocopa. 



4. Two or more females use a common hole of refuge : 



Panurgus, Halictus, etc. 



(b) The mother survives to see the brood and watches 

 over the nest. 



5. Halictus sexcinctus. 



6. The cells form a comb, Halictus quadricinctus. 



7. The first-born young are all females, they work in 



the old nest, and parthenogenetically produce 

 males and females : Halictus scabiosus. 



8. The next stage, according to Buttel-Keepen, should 



be that in which the mother and the parthenogene- 

 tically reproductive young work together in the 

 old nest, but a representative of this stage has not 

 yet been found. 

 II. Bees living socially : 



9. The fertilized female hibernates alone ; forms in 



Spring a new nest ; is helped by a brood of workers 

 which are parthenogenetically reproductive only 

 in isolated cases ; and produces in the course of 

 summer males and more females. In autumn the 

 whole society dies off except the fertilized females : 

 Humble-bees. 



10. Permanent societies, with imperfect combs : the 



tropical species of Melipona and Trigona. 



11. Permanent societies, with perfect combs : Apis 



mellifica, A. dorsata, A. florea. 



This very interesting series does not of course disclose 

 the impulses which led from one mode of life to another, 



