New mayfly species of Caenis and Kalimaenis from Thailand and descriptions of two new genera of the subfamily Caeninae (Ephemeroptera: Caenidae)

Six new species of Caenis from Thailand are described herein: Caenis ludovicin. sp., Caenis nasutan. sp., Caenis longiforcipatan. sp., Caenis karenaen. sp.,Caenis obtusostilatan. sp. and Caenis acutostilatan. sp., as well as the larvae of Caenis picea Kimmins, 1947 and Caenis ulmerianaMalzacher, 2013, which were so far only known as males. Furthermore, a new species of the genus Kalimaenis, Kalimaenis proceran. sp., is described. Also described from the same area are two new genera of the subfamily Caeninae: Elatosaran. gen. (Type species Elatosara phanomensisn. sp.) most probably belongs to the tribe Clypeocaenini; Thainisn. gen. (Type species Thainis kalimaenoidesn. sp.), is classified within the tribe Caenini. The phylogeny of the new genera is discussed. A larval key to the Caeninae from Thailand is provided and the key to the male Caenis of the Oriental region (Malzacher 2015) is replenished.