Abstract
BACKGROUND: The tribe Xyleborini comprises over 1,300 species of ambrosia beetles, all of which form mutualistic relationships with fungi. Several beetle species exhibit strong host preferences, particularly within the plant family Fagaceae for genera such as Castanopsis. This study documents the xyleborine beetles associated with Castanopsis inermis in Thailand to improve understanding of their host use and diversity. NEW INFORMATION: Twenty species of xyleborine ambrosia beetles were collected from a single fallen Castanopsis inermis tree. Amongst them, twelve species were recorded from C. inermis for the first time. One species, Arixyleborus perbrevis Sittichaya & Smith, sp. nov., is described as new to science, while Cnestus ater (Eggers 1923) is newly recorded from Thailand. Some biological observations on xyleborine ambrosia beetles are also presented.