342 ENTOMOLOGICAL NEWS [Nov.,'l8 



exceptions. But as regards the exceptions, the presumption is 

 that the observations are incomplete. Accordingly the average 

 flight given in the table is too short for the females and the 

 species. 



As a rule the early groups have a shorter flight than the 

 late ones : the Andrenidae than the Panurgidae, the Osmiinae 

 than the Megachilinae, Nomadidae than other Melectoidea, 

 Tetralonia than other Euceridae. But Prosopis has a longer 

 flight than Collctcs, and the Dasygastrae, although earlier, 

 have a longer flight than the other long-tongued bees. 



In the case of 72 Pygidialia : 23 short-tongued species have 

 an early maximum and average 56.1 days; 27 long-tongued 

 hosts have a late maximum and average 68.0 days ; while 22 

 long-tongued inquilines average 61.6 days. In the case in 

 which the inquilines are known they have a shorter flight 

 than their hosts. 



As regards their beginning, the Andrenidae are quite pe- 

 culiar, so that they essentially modify the general result. Com- 

 pare : 



Begin 

 Males and 

 Males females 

 first together 



Andrenidae 42.5 30.0 



Other bees 76.3 7.6 



According to Schmiedeknecht (Loew /. c.) Andrcna clark- 

 clla is proterogynous. According to my observations the local 

 species fall into the following three sets : 



Proterandrous: Andrena erythronii, salicacea. sayi. erythrogastra. 

 pruni, dunningii, geranii, Ptilandrena g. maculati, Opandrena cressonii, 

 Trachandrena forbesii, rugosa, crataegi, Pterandrena krigiana, rud- 

 beckiae, pulchella, helianthi, asteris. 



Synchronous: Andrena salicis, carlini, illinoensis, nubecula, salic- 

 taria, platyparia, Ptilandrena polemonii. Parandrena andrenoides, 

 Opandrena personata. ziziae, Trachandrena claytoniae, Pterandrena 

 solidaginis. 



Proterogynous: Andrena mandibularis. nasonii. Ptilandrena eri- 

 geniae, lomelissa violae, Opandrena bipunctata. serotina, Trachandrena 

 mariae, nuda, hippotes, spiraeana, aliciae. 



