Abstract
Based on historic collections and new material from Sumatra and Java, the species Rhithrogeniella ornata Ulmer, 1939, type species of the genus Rhithrogeniella, is reinvestigated. The nymph is described for the first time and is closely related to the continental Southeast Asian species Rhithrogeniella tonkinensis Soldán and Braasch, 1986. Rhithrogeniella belongs to the subfamily Ecdyonurinae, and is related to the genera Nixe Flowers, 1980 and/or Paracinygmula Bajkova, 1975 based on characters of the nymphal stage. Species described from Taiwan in the genus Nixe are transferred to the genus Rhithrogeniella: Rh. littoralis (Kang and Yang, 1994) comb. n., Rh. mitifica (Kang and Yang, 1994) comb. n. and Rh. obscura (Kang and Yang, 1994) comb. n.
Highlights
Ulmer (1939) established the genus Rhithrogeniella to accommodate the species Rhithrogeniella ornata Ulmer, 1939 known from imagos and subimagos from Java and Sumatra
In the key to the genera (Ulmer 1939), Rhithrogeniella is keyed with the genus Afronurus Lestage, 1924 from which it differs by the tarsal composition of the foreleg
The presence of a transverse suture on the mesonotum together with the shape of the depression of the furcasternum indicates that Rh. ornata cannot be a member of Rhithrogeninae; it is not a synonym of Rhithrogena as suggested by Wang and McCafferty (2004)
Summary
Ulmer (1939) established the genus Rhithrogeniella to accommodate the species Rhithrogeniella ornata Ulmer, 1939 known from imagos and subimagos from Java and Sumatra. According to Ulmer (1939), the genus was characterized by genitalia resembling those of Rhithrogena, with two simple lobes lacking spines or titillators. The other hand, the new genus differed from Rhithrogena in the tarsal proportions on fore- and hind legs. In the key to the genera (Ulmer 1939), Rhithrogeniella is keyed with the genus Afronurus Lestage, 1924 from which it differs by the tarsal composition of the foreleg. During the following years, nothing substantial was added to the knowledge of the genus, and keys which included Rhithrogeniella were based on Ulmer’s description and drawings (Tomka and Zurwerra 1985; Tshernova 1974)
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