510 A CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



Drs. J. R. Traver, J. McDiinnough, and H. T. Spieth have contributed ex- 

 tensively to the knowledge of American species. Dr. Traver is best known as 

 the author of the systematic section of The Biology of Mayflies. Dr. McDun- 

 nough has described more North American species than any other person, and 

 Dr. Spieth is well known for his phylogenetic studies. 



The difficulties of collecting and preserving mayflies have resulted in im- 

 portant collections being established only by specialists in the group. A suc- 

 cession of specialists have built a fine collection in the British Museum (Natural 

 History). Lestage's collection can now be found in the Institut Eoyal des Sci- 

 ences Naturelles de Belgique, while it appears that Navas scattered his collection 

 among many museums. Although Ulmer has an extensive personal collection, 

 much of his work has been based on material from various European museums, 

 especially the ones in Berlin and Hamburg. The collection established at the 

 Museum of Comparative Zoology at Cambridge is rich in North American types, 

 as are the Canadian National Collection and the Cornell University Collection. 



The recognition of distinct groups within an ancient and apparently declin- 

 ing order such as the Ephemeroptera is not particularly difficult, but because 

 the order is small there has been a continued reluctance to give familial rank 

 to these groups. Such groups have consistently been utilized as the "working 

 units" of the classification, even though they have been ranked as sections, tribes, 

 subfamilies, or families. The history of the recognition of the various groups is 

 relatively simple, but the story of the rank accorded such groups is indeed com- 

 plex and often bewildering. 



The division of the order Ephemeroptera into groups usually regarded as 

 families at present started with Eaton's revisional monograph. Of his fourteen 

 sections, twelve have been raised subsequently by various workers to the rank 

 of family. Thus to Eaton's original arrangement can be traced the families 

 Palingeniidae, Ephoridae (= Polymitarcidae), Ephemeridae, Potamanthidae, 

 Leptophlebiidae, Ephemerellidae, Caenidae, Prosopistomatidae, Baetidae, Siph- 

 lonuridae, Baetiscidae, and Heptageniidae (=^Ecdyonuridae). 



In 1913 Bengtsson proposed that the genera Ametropus and Mctretopus be 

 considered as constituting a separate family, Ametropodidae, and in 1914 Georg 

 Ulmer recognized the distinctness of, and named, the family Oligoneuriidae, a 

 group formerly included in the Palingeniidae. 



In the standard American work The Biology of Mayflies, Needham applied 

 subfamily rank to the recognized families of European authors. The family 

 Ephoridae (= Polymitarcidae) of the Europeans was divided into two sub- 

 families, Ephorinae and Campsurinae, the Ametropodidae divided into Ame- 

 tropodinae and Metretopodinae, and a new subfamily Neoephemerinae, was 

 proposed. 



Balthasar (1937) removed Arthroplea from the Heptageniidae and placed 

 it in a separate family, Arthropleidae. The soundness of such a move, however, 

 remains to be proved. In the year 1938, Tshernova, and Motas and Bacesco in- 

 dependently proposed the family Behningiidae for the inclusion of the unusual 

 genus Behningia, first described by Ulmer and later named by Lestage. The 

 same year Lestage considered Behningia to be a member of the Oligoneuriidae 

 and reduced Behningiidae to synonymy of Oligoneuriidae. Demoulin has re- 

 cently reinstated, I believe correctly, this monotypic family. In 1938, Lestage 



