New species of Nigrobaetis from Southeast Asia (Ephemeroptera, Baetidae)

Abstract

Based on larvae collected in the Philippines, Borneo (Kalimantan), Sumba, and Sumatra, the presence of the genus Nigrobaetis in the Philippines and Indonesia is reported for the first time. Six new species are described and illustrated, two from the Philippines and four from Indonesia. A larval key to all Nigrobaetis species of the Philippines, Indonesia and neighbouring continental Southeast Asia is provided, morphological differences to the species of Taiwan are discussed as well. The eggs of three new species are described, and the morphology of the eggs of Nigrobaetis is briefly discussed.

A new, widespread genus of Baetidae from South Asia (Insecta, Ephemeroptera)

“… Nigrobaetis s.l. has no arc of setae on paraglossae and usually has short denticles between prostheca and mola of left mandible or a smooth margin ( Müller-Liebenau 1984 ; Kaltenbach and Gattolliat 2023 ); only in rare cases, there is a medium tuft or short row of setae close to prostheca of left mandible ( N. colonus Gattolliat, 2004; N. cryptus Gattolliat, 2004; N. terminus Chang & Yang, 1994) ( Kang et al 1994 ; Gattolliat 2004 ). Further, Arcobaetis gen. nov. has very slender legs with femora length 4–6× maximum width, outer margin of femora with a row of short, spine-like setae, and claws with distal denticles larger and directed distad and proximal denticles minute.…”

“… Nigrobaetis s.l. usually has less slender legs, outer margin of femora with a row of long, spine-like setae (apart from some Alainites and Takobia that also have short, spine-like setae at outer margin of femur), and claws with denticles gradually decreasing in size toward base or exceptionally without denticles ( Müller-Liebenau 1984 ; Sroka et al 2021 ; Yanai et al 2022 ; Phlai-ngam et al 2022b ; Kaltenbach and Gattolliat 2023 ). Additionally, the larvae of Alainites are distinguished by a paraproct with an elongated prolongation, and the prostheca of the right mandible is bifid, reduced to two bristle-like feathered appendages ( Yanai et al 2022 ), both cha­racters are absent in Arcobaetis gen. nov.; the larvae of Takobia have a paraproct with a short, bent prolongation and a right prostheca reduced to split bristles ( Sroka et al 2021 ), whereas these characters are absent in Arcobaetis gen. nov.…”