Abstract: Ultrastructure and secretory function of the mesodermal reproductive tract and acessory glands in the adult male black cutworm, Agrotis ypsilon, were studied with light and electron microscopies and histo-chemical method. The results were summarized as follows: (1) The male mesodermal reproductive tract was divided into eight regions: sperm modification vesicle, vas deferens, seminal vesicle and spermatophore gland in 1-5 segments, based on the constriction location, anatomical characters, ultrastructure, secretory manner and sperm variation in both form and amount.(2) The histological structure of male mesodermal reproductive tract showed it consisted of four layers: single epithelum, basal lamella, muscle layer and peritoneal membrane, but without a cuticular intima. (3) The secretory cells of the tract and gland had good capacity for protein synthesis and secretion. They were classified into two main types on the basis of organelles in the cytoplasm: (a) endoplasmic reticulum type, which had a lot of rough endoplasmicreticula and Golgi complexes; (b) vacuole type, which had a great number of secretory vacuoles and free ribosomes. There were at least four secretory manners in these cells,I. E. granular apocrine, vacuole apocrine, cytoplasm merocrine and intercellular secretion.

Key words: Agrotis ypsilon, male accessary glands, reproductive tract, uhrastructure, secretory manner