Deutsch. Ent. Zeitschr. 1909. 



551 



New Ephemeridae from Denmark, Arctic Norway and 

 tlie Argentine Republic. 



By Esben Petersen, Silkeborg (Denmark). 



(With 12 Figures.) 



1. Cl eon J ör g ens eni n. sp. 



Imago. cf. Turbinate eyes brownish red; the lower eyes 

 black. Mesothorax pitchy brown, dorsally and ventrally. Abdomen 

 above light brown , ventrally paler. Femora light brown, tibiae 

 and tarsi pale yellowish brown. Knees and terminal tip of tibiae 

 brown. Wings hyaline with a faint yellowish brown tint, espe- 

 cially on the front margin. Costa, subcosta and radius distinct 

 and yellowish brown ; the other longitudinal nervures hardly 

 visible. Forceps yellow. Setae yellow with a faint brownish 

 tint ; joinings scarcely distinct. 



Fig. 1. 

 Forceps of Cloeon Jörgen 



Fig. 2. Wing of Cloeon Jörgenseni. 



5. Eyes dark. Mesothorax above and below pitchy brown. 

 Abdomen brown red , a little paler ventrally and towards apex. 

 Femora light brown, tibiae and tarsi pale yellowish brown, knees 

 darker. Wings as in the male. 



S u b i m a g 0. Head brownish grey, eyes dark. Mesothorax 

 above pitchy black , below light greyish brown. Abdomen dor- 

 sally brown, ventrally pale greyish yellow. Wings grey. 



Long. 4,5 — 5 mm ; wing 5 — 6 mm ; setae 10 — 14 mm. 



Chacras de Coria, Mendoza, from March to October, P. J ö r - 

 g e n s e n leg., in alcohol, in my collection. 



The forceps of C. Jörgenseni differ in character from those 

 of C. brunmum (or from the normal type) very much in the same 

 manner as the forceps of Centroptilum tenellum and Baetis niger 

 differ from those of their congeners. 



2. Cloeon hrunneum n. sp. 



I m a g 0. cf • Turbinate eyes light brown with the circum- 

 ference narrowly dark brown ; the lower eyes bluish grey. Pro- 



