MICHENER: THE APOIDEA ^jj 



believed that the presence or absence of this plate was a primary character di- 

 viding bees into two great natural groiips. In fact, he went so far as to suggest 

 that the pygidialate and apygidialate bees might have arisen from pygidialate 

 and apygidialate specoid wasps, respectively. This classification had many merits 

 but unfortunately Robertson, working with a limited fauna, did not realize that 

 the pygidial plate could be independently lost in various groups. 



Borner devised another classification in 1919, based primarily on mouth- 

 parts. Like the other classifications which utilize chiefly one set of characters, 

 this resulted in some artificial arrangements. 



A serious attempt to use all available characters was made by the present 

 author in 1944. The result was a classification quite different from previous ones. 

 It is to be hoped that as more characters are discovered and utilized, this clas- 

 sification will be modified to refiect the added knowledge thus obtained. 



Bionomics 



Most students of bees have been interested in bionomics of these insects. 

 That a considerable amount of information on this subject was available for 

 European species a century ago is shown by leafing through Part I of F. Smith's 

 Catalogue of British Hymenoptera in the Collection of the British Museum 

 (1855). Subsequent work has mostly been done in Europe, with German work- 

 ers taking the lead in work on social Halictidae, Italian workers (especially 

 Guido Grandi) on larval characters, with individuals of all principal nations 

 contributing papers on nest-making and habits of various groups. Outstanding 

 among students in this field was Malysliev. In America work on wild-bee biology 

 has lagged almost until the present time, although several workers are now in- 

 terested in such studies. 



The importance of bees in cross pollination of various plants has been long 

 understood, but only within the last fifteen years has the superiority of certain 

 solitary forms over the honeybee for pollination of some crop plants been real- 

 ized. This realization has provided a stimulus to the study of bionomics and 

 several persons are now investigating these matters in the hope of solving prac- 

 tical pollination problems. 



Some groups of bees of special interest for various reasons have received a 

 great deal of attention. Outstanding, of course, is the honeybee, upon which 

 much has been written. No discussion of this sort would be complete without 

 mention of the famous studies by von Frisch, still under way, on the behavior 

 and sense physiology of this insect. Another major group of social bees, the 

 Meliponini, has received consideralile study, for example from von Ihring in 

 Brazil and more recently from H. F. Schwarz in this country and Warwick E. 

 Kerr in Brazil. 



The Future 



The lines of investigation which now seem important for further study 

 among bees are numerous. For example it seems certain that among the Halic- 

 tidae every gradation between solitary and thoroughly social forms will be 

 found and that studies of this grading series will shed light on the steps in de- 



