8i2 THE AMERICAN NATURALIST. 



Wiener Entomologische Zeitiing, Vol. XIII, pp. 271-284, and 

 PI. II, Figs. 8-13, gives an exhaustive discussion of the whole 

 subject, with citations of the other authors and extracts from 

 their papers. According to Mik, who had abundant opportuni- 

 ties for observation, the male produces a real web which is 

 borne by the hind feet and serves to assist the fly in the some- 

 what peculiar gyrations of its flight. The different nature of 

 the structure makes it unnecessary to go into further particu- 

 lars here. 



The species to which our observations pertain was sent to 

 Professor Wheeler, of Chicago, who has been studying the 

 family for several years, and identified by him as Empis 

 poplitea Loew, " or a closely related species," 



The use of the term "balloon" should not be taken to imply 

 that the structure described is lighter than air. 



