Abstract
Mayfly larvae and imagos were collected at approximately 50 localities of the Kingdom of Saudi Arabia (KSU). Included in this material, three species of Labiobaetis Novikova & Kluge, 1987 are recorded, two of them being new to science. Labiobaetis potamoticus Gattolliat & Al Dhafer, sp. n. is described from both larvae and adults, whereas Labiobaetis alahmadii Gattolliat & Al Dhafer, sp. n. is only known from the larval stage. The two species are compared morphologically with Palearctic and Afrotropical species of Labiobaetis. A third species, Labiobaetis glaucus (Agnew, 1961) is reported for the first time from the Arabian Peninsula. The species was originally described from South Africa and subsequently reported from the east and northeast of Africa. A molecular reconstruction including 18 Afrotropical and Palearctic species of Labiobaetis was performed using 658 bp of the mitochondrial gene CO1. The reconstruction highly supported the validity of the two new species and confirmed the occurrence of L. glaucus in KSU.