372 Annals Entomological Society of America [Vol. VI, 



4. The evolution of the adult in which specialization is 

 shown by changes of function and developments for the fur- 

 therance of reproduction. 



5. Adjustments for aquatic situations shown in the struc- 

 tures of the eggs. 



6. A Bibliography of biological, morphological, and the 

 more important systematic works dealing with this group. 



II. HISTORICAL. 



In the following historical sketch I have tried to select 

 the more important papers of biological significance. In 

 many cases, however, systematic, morphological, and biological 

 work have been so closely related that such a separation has 

 been impossible. 



Swammerdam. 1661. The foundation study of the bio- 

 logy of May-flies was made by Johann Swammerdam, at 

 Culenburg, on the Rhine, in 1661. As a field naturalist, 

 he learned the most important facts concerning the life of 

 Ephemerus, (probably Palingenia longicauda Oliv.). As an 

 anatomist he dissected and studied its internal and external 

 structure with great care. He described the emergence of 

 the nymph, the sub-imago stage in males, and the final or 

 imago stage in which he believed that the eggs and the sperm 

 were deposited separately in the water. He concluded that 

 no food was taken during aerial life, and that copulation did 

 not occur. He examined the eggs and tested their power of 

 dispersal by letting them fall into the water from the end of a 

 knife. His work is a remarkably truthful and interesting 

 record. Later works have added and corrected, but none 

 have contributed better biology. 



Reaumur. 1742. In Memoires des Insectes, 1742, Reaumur 

 reviewed much which had already been told by Swammerdam, 

 and illustrated more profusely the life history of a burrowing 

 May-fly, probably also Palingenia. Some of Reaumur's obser- 

 vations were made upon nocturnal species. After he had 

 noticed them swarming about a light near the river bank, 

 he placed a tub of water in his own garden. By holding a 

 light above this, in the evening, he was able to gather great 

 numbers of May-flies and to watch their transformation from 

 the sub-imago to the imago stage, and to see them lay their 



