Occasional Papers of the Museum of Zoology 5 



flowing stream at another season. And miles of lagoons may 

 a few years before have been part of a swift-flowing river. 

 In the first case a dragonfly species on the wing throughout 

 the year may occupy the habitat because of conditions at a 

 certain season, though other seasons bring conditions incon- 

 gruous with the general preferences of the species ; and in 

 the second case, a species may survive at least for some time 

 in the lagoon, though its preferences are for the stream from 

 which the lagoon was formed. 



Some dragonflies, such as the Trameas, mentioned above, 

 and there are many others, range far and wide. Others, such 

 as the Enallagmas, apparently live their lives practically in 

 one habitat. But that this is only apparent is obvious when 

 one considers the sudden appearance of large numbers of 

 Enallagmas at rare interv-als at a small, isolated swamp, sur- 

 rounded by forest, with no known habitats of the same species 

 within fifty miles or more. The known distribution of many 

 species of apparently very circumscribed habitats also bears 

 this out. 



Species of Hetaerinas.. are dragonflies of a very circum- 

 scribed habitat, and no others known to me during imaginal 

 life apparently remain closer to the location where their eggs 

 are laid and where their nymphal lives are passed. As to 

 how the distribution of the species of the genus has come 

 about we know as little as we do of the origin of the species 

 themselves. But taking this into account, I know of no other 

 genus in the order where one may more safely record obser- 

 vations on habitats with some certainty that such observations 

 are definitely descriptive of the species observed, and not th5 

 record of some mere accident in the life of the species. As 

 an example of the latter kind, I might mention the discovery 

 of a number of larvae of Pantala hymenaea successfully living 



