Abstract: This paper describes the spermatozoon ultrastructure in Mecopoda nipponensis (De Haan). Spermatozoon of this species were examined by transmission electron microscopy after double fixation of live material in glutaric-aldehyde and osmic acid. Its acrosomal complex lies to the side of the flat, dense nucleus and partially embraces it. Two broad bean shaped accessory bodies are located laterally to the axoneme, which is of a typical 9+9+2 pattern. Two almost completely crystallized mitochondrial derivatives are oval in cross-section. There are three connecting bands between mitochondrial derivatives and axoneme. Two flat membranous cisterns close to mitochondrial derivatives are S-shaped in cross-section. A character peculiar to this species, an additional bi-layer membrane, appears around organelles of the tail in some cross-sections.

Key words: Orthoptera, Mecopodidae, Mecopoda nipponensis, spermatozoon, ultrastructure