Lasioglossum (Evylaeus) subtropicum sp. nov. is a eusocial halictine bee recently discovered on lriomote Island. It is similar to some species of the L. (E.) fulvicorne group s. Iat., particularly to L. sibiriacum (Bluthgen) and L. baleicum (Cockerell), but is peculiar by the propodeal dorsum not distinctly carinate at the end. Comparison with some other social halictines shows its conspicuous size difference between queen and worker than in these species. Bionomics of this species will be described in a separate paper.
Key words: Morphometry; social bees; Lasioglossum subtropicum sp. nov.; Iriomote Is.