Vol. Xxix] ENTOMOLOGICAL NEWS 34! 



Begin 

 Males and 



Males females Females 



first together first 



69.0 12.5 18.5 



End 



Males and 



Females females Alales 



last together last 



87.5 2.1 10.3 



The females are first in only 18.5 per cent, of the cases and 

 the males last in only 10.3 per cent. 



The males were observed first in 127 cases and the females 

 last in 161. This accords with the probabilities, for the males 

 average 9.6 days before the females, while the females average 

 22 days later than the males. 



In 112 cases, 60.8 per cent, of those in which both sexes 

 are known, the males are first and the females last. Of these 

 109 are taken as about correct, and normal, and three are ex- 

 cluded here as incomplete. The following table gives the num- 

 ber of normal species in each group and the average number 

 of days under each heading: 



Nor- Males Females Spe- 



mal precede follow Males Females cies 



Prosopis 3 11.3 21.0 143.0 152.6 164.0 



Colletcs 7 6.5 15.5 63.7 72.7 79.2 



Andrenidae 16 6.8 22.5 33.6 49.4 56.2 



Other short-tongued bees 7 6.0 26.1 29.8 50.0 56.0 



Osmiinae 10 10.6 28.0 44.3 61.7 72.3 



Megachilinae 10 6.5 25.1 63.8 82.4 88.9 



Coelioxys 4 12.2 20.2 65.5 73.5 85.7 



Stelididae 3 18.0 21.3 53.6 57.0 75.0 



Nomadidae 1 1 9.1 22.2 35.8 49.0 58.0 



Epeolidae and Melectidae ... 11 10.0 17.5 47.4 55.0 65.0 



Tctralonia 4 3-7 14-0 37-2 47-5 51-2 



Other Euceridae 18 10.8 12.1 59.0 60.2 71.1 



Other long-tongued bees 5 10.4 17.8 58.4 65.8 76.2 



Total 109 8.9 20.1 50.8 62.0 71.1 



The males fly a shorter time before the females appear 

 than the females do after the males disappear, and conse- 

 quently have a shorter flight. In 109 cases there are only 27 



