Notes on the Genus Erythemis 5 



as permanent ponds, and since during the dry season the imagoes are numer- 

 ous, it is very probable that the larval life is brief, and it is not improbable 

 that the dry season is bridged by imagoes rather than by drought resistant 

 eggs or larvae. We know that old and worn females, which might well have 

 lived throughout the dry period, are still able to oviposit ; and we know that 

 when dry depressions become pools with the coming of the rainy season ovi- 

 positing individuals of species of several genera, including Erythemis, imme- 

 diately put in an appearance. 



It is not improbable that species of dragonflies whose larval life is spent 

 in temporary pools and whose imaginal life is continued during the dry sea- 

 son are less bound to the vicinity of the location of these pools than are spe- 

 cies whose larval life is spent in permanent bodies of water and which would 

 therefore develop a stronger fixed habitat tendency through numberless gen- 

 erations of larvae and adults attached to a particular habitat. A longer larval 

 life might also strengthen this tendency. It may be safely concluded that 

 dragonflies emerging from temporary pools after a short larval life and with 

 a long imaginal life, under favorable conditions for extended flight (the drv 

 season in the tropics) before them, will be wide wanderers, and, other con- 

 ditions permitting, species of wide distribution. 



So far as species of Erythemis are concerned, temperature is not a limit- 

 ing factor over the large area included in tropical America. Swamps, ponds, 

 pools, and lakes of varied characters, permanent and temporary, are abun- 

 dant and widely scattered over this region, forming, with the exception of 

 the southwest coast of South America, a practically continuous habitat. Spe- 

 cies of Er}'-themis as imagoes are active and conspicuous, apparently living 

 happy, care-free lives so far as predaceous enemies are concerned. They 

 are voracious feeders on a varied diet of other insects, including species 

 which are not dependent on bodies of water during their own lives, such as 

 Lepidoptera. Hence, they can find a living anywhere and are not held to the 

 immediate vicinity of their birthplace, as are many species whose imaginal 

 food consists largely, if not entirely, of aquatic insects, and whose adaptability 

 to a varied diet may be Hmited. Because of their larval life in both tempo- 

 rary and permanent pools, individuals are numerous as compared with other 

 simliar species whose larval life is confined to permanent pools, and, at the 

 time of ovipositing, when active competition takes place, the males of one 

 species protecting their own females against attacks and at the same time 

 hustling away from the water the females of other species, Erythemis, because 

 of its numbers and activity, is at no disadvantage. The eggs of Erythemis 

 are dashed in the water and oviposition is as safe against parasitism of the 

 eggs as it is in the other large number of species of similar habit. There is 

 no reason to think the larvae of Erythemis are exposed to any particular 

 danger. Their use of temporary pools would relieve them of competition 

 or attack of many forms of aquatic life, while their successful use of perma- 

 nent pools indicates they can meet the conditions there. 



From the above considerations, we can understand the wide distribution 

 of species of Erythemis which have been able to cross the great river valleys 

 of South America, which valleys, marking frequently the broad areas which 



