The male and female of Psychodopygus leonidasdeanei n.sp., (Diptera : Psychodidae) are described and illustrated from specimens collected in Shannon traps near Santarem, Para State, Brazil. This species is a member of the squamiventris series and information is given on the distribution of the members of this series in Para. A pictorial guide to separate the males and some females from others in the series is given.