A new character for identifying larval instars of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)

Abstract Three larval instars of Prostephanus truncatus (Horn) were recognized in rearings at 25°C and 75% r.h., based on the greatest distance between the ventrally sclerotized lateral structures of the frontoclypeus. This distance for the first, second and third instars averaged 0.135, 0.183 and 0.274 mm, respectively. Larvae can be measured under ethanol by this method; mounting on slides, a prerequisite for measuring head capsule width, is not required.