144 NOTES ON ANTHOPHORA ABRUPTA 



1919, showed that the cells contained pupae. The period of 

 pupal formation undoubtedly varies somewhat from year to 

 year in direct correlation with climatal conditions. Under 

 laboratory conditions the larval stage may be shortened and 

 pupae formed about the first of March. On March 13, 1920, 

 I brought into the laboratory some cells containing larvae 

 which since the time of collection had been kept out of doors 

 under approximately natural conditions. One of these cells 

 contained a pupa on March 29. Other larvae in cells placed on 

 September 20, 1919, under warm laboratory conditions, began 

 to pupate in the early part of March. Such a forced expediting 

 of the transformations under the influence of prematurely warm 

 conditions apparently has a weakening effect, for an adult male 

 emerging on March 18 died soon after escaping from his cell. 

 Cells brought into the laboratory in Spring produced, however, 

 adults of normal vitality. 



The pupal stage is of short duration. Freshly transformed 

 pupae collected at Oakwood on May 31, 1919, began to produce 

 bees on June 7 and continued to do so until June 14. As the 

 pupal stage nears completion the pupa gradually becomes 

 darker and darker until the adult emerges. The emerging 

 adults dig their way from the pupal cells with the aid of their 

 stout mandibles. The males appear in advance of the females, 

 as shown by both laboratory and field observations. Of the 

 bees reared indoors in 1919, two males emerged on June 7, four 

 males on June 8 and twenty-six more of the same sex on June 9. 

 On June 11, eleven females emerged and enough more males to 

 bring the total for that sex up to one hundred and four indi- 

 viduals. Females continued to appear until June 14, a total of 

 sixty-five altogether. Cases of proterandry similar to this one 

 seem to be quite common among bees, as was pointed out by 

 Robertson (1918). Not only do the males appear first but in 

 the colony I studied they dominated numerically by a ratio of 

 about two to one. Observations at Oakwood in 1919 and 1920 

 confirmed my laboratory observations. On July 3, 1919, I 

 visited the Anthophora bank and found a veritable swarm of 

 female bees hovering al)out the })ank and entrances to the ]:)ur- 

 rows. Apparently I was just a little too late to see the males 

 holding forth })cfore the bank. On June 26, 1920, at the same 



