Immature stages and morphology of Haplogaonatopus atratus ESAKI et HASHIMOTO were investigated. The experiments were conducted at 24℃ under 16 hours lighting.
The egg is smooth creamy white, and curved slender elliptical in shape. The larva is separated into four types by the morphology of it. The 1st-3rd type larvae cannot discrminate between head and abdomen by their appearence, but located a pair of fleshy oral lobes at anterior parts of their body. Drawing the frequency dlstribution of cephalic oral lobe-height of the 1st-3rd type larvae and head-width of the 4th type larvae, there are five larval instars, and the 1st type larvae are separated into two instar stages. The first four instar larvae inhabit in the hosts, but the 5th instar larva hatches from the host and moves about freely for a short time untill it spins a cocoon. A larval sac, the part of the larva protruding from the host, is present in the 3rd and the 4th instars.