Effect of the Parasite Copidosoma truncatellum1 on Development of Its Host Trichoplusia ni2

Parasitism of larvae of Trichoplusia ni (HÜbner)by Copidosoma truncatellum (Dalman) caused 33 to 58% of the T. ni larvae to undergo a supernumerary molt, regardless of whether the host was from a normal culture which pupated at the end of the 5th or 6th instar. Parasitized larvae which did not enter a supernumerary instar gained weight significantly faster and had greater head capsule sizes than unparasitized larvae. Parasitized larvae which entered a supernumerary instar gained weight more slowly and possessed smaller head capsules than unparasitized larvae, except for the supernumerary instar, which had a significantly greater final weight and head capsule size than achieved by unparasitized larvae.