Notes on the Genus Erythemis 17 



It is entirely conceivable that a single fertile female in a certain instance 

 might furnish the entire original Hetaerina invasion of the headwaters of 

 some small mountain creek. Here the species, by direct descent from this 

 single female, might maintain itself without any admixture of new blood for 

 many generations. After a period of time, the infrequent and accidental 

 invasion by new blood would be quickly swamped in the mass of old stock. 

 Individuals of Erythemis, on the other hand, are wanderers, and the Ery- 

 themis fauna of any pond may be partly or largely descended from new immi- 

 grants of the preceding season, their descendents in turn scattering with the 

 dry season and many of them visiting other ponds when the period of ovi- 

 , positing comes. 



Specimens of any species of Erythemis are remarkably uniform through- 

 out the range of the species. I know of only one exception, that of the 

 Guatemalan specimens of H. mithroides, which are distinctly larger than 

 South American specimens of the same species. On the other hand, a num- 

 ber of cases of differences in a species of Hetaerina in its range can be cited. 

 The most striking case I recall is the remarkably large, dark specimens of 

 crucntata occurring at a high elevation in the isolated Santa Marta Moun- 

 tains of Colombia. Almost equally striking is the large, dark form of macro- 

 pus at an elevation of 2,230 feet in Peru. On a larger scale, but less dis- 

 tinctly marked, are the pale forms of caja and macropus east of the Andes 

 in western Venezuela, as compared with the dark forms west of these 

 mountains. 



LocAijTiEs Not Heretofore Described in This or Other Papers 



1. Bejuma, Department of Caraboba, Venezuela. In describing the coun- 

 try about Bejuma in Occasional Papers, No. 130, several swamps or shallow 

 ponds which lie in the valley were not mentioned. One of these is about one 

 mile east of Bejuma. The area is about an acre, surrounded by thorny 

 mimosas inside which grew several species of sedges, water hyacinth, another 

 aquatic with three yellow petals, orange at the base, another with small pur- 

 ple flowers, and a small yellow Utricularia. This pond was in the last stages 

 of drying up when we saw it on February 16, 1920, with very little open 

 water, which had a maximum depth, with the mire in which one sank, of 

 about three feet. 



2. Encontrados, Department of Zulia, Venezuela. Encontrados is on 

 the right bank of the Catatumbo River and is the lower terminus of the Gran 

 Ferrocarril del Tachira. Its elevation is about 138 feet, and it lies in a low, 

 flat country of brushy forest, large areas of which near town and along the 

 railroad are now in grass, bananas, cocoa, and some sugar cane. Just above 

 town is a long lagoon filled with aquatics and bordered with brush and pas- 

 tures where odonate life, especially strong-flying libellulines, was very abun- 

 dant. Along the river below town are many flats, covered with water during 

 the rainy season, and during the dry season consisting of stretches of mud. 

 grass, and bushes, with shallow pools. Three or four kilometers below town 

 on the left river bank is a caiia eight to twelve feet wide, mostly in the sun, 



