Abstract
Three new species of Trichosetodes, namely T.carmelaesp. nov., T.katiengensissp. nov. and T.ratanakiriensissp. nov. are described and illustrated by male specimens. The male genitalia of T.carmelaesp. nov. can be distinguished from the other 16 species of the genus found in Southeast Asia by the shape of the phallicata. The phallicata of T.carmelaesp. nov. bears a tuft of long hairs in the middle of the dorsal edge. Trichosetodeskatiengensissp. nov. can be distinguished from the other species in Southeast Asia by the shape of the phallicata which is divided into dorsal and ventral branches in lateral view, and T.ratanakiriensissp. nov. by the characters of the left inferior appendage and the shape of segment IX. The posterior end of the left inferior appendage of T.ratanakiriensissp. nov. is not forked and the ventral and lateral views of the posteroventral lobes of segment IX are rounded. Illustrations of male genitalia of Trichosetodeskampongspeuensis Malicky & Kong, 2020 are provided for comparison. The molecular diversity of new Trichosetodes species was analyzed using the mitochondrial large subunit ribosomal rRNA gene region (16S rRNA). In terms of their genetic divergence, T.ratanakiriensissp. nov. and T.kampongspeuensis exhibited remarkable proximity, with only a 1.4% distance. On the contrary, T.carmelaesp. nov. displayed genetic disparity exceeding 6.3% when compared to both T.ratanakiriensissp. nov. and T.kampongspeuensis.