Effect of Host Age on Progeny Production of Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae) Reared on Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae)

Abstract

Five host ages of Maize weevil, Sitophilus zeamais (Motschulsky) reared on brown rice were examined for progeny production of Theocolax elegans (Westwood). Brown rice kernels infested with S. zeamais were exposed to a mated female of T. elegans after 13, 15, 17, 19 and 21 d following S. zeamais introduction. Host stages were determined by measuring head-capsule widths from all the host ages. There was a signifi cant difference (P < 0.05) in T. elegans progeny production among the different host ages. Total progeny, total female progeny and total male progeny produced by 19-day-old S. zeamais larvae were signifi cantly higher (P < 0.05) compared to the other host ages. Progeny of T. elegans raised on 19-day-old S. zeamais larvae had a higher female to male ratio compared to the other host ages. Sitophilus zeamais larvae after 13, 15–17 and 19–21 d were found to be second, third and fourth instars, respectively. It was concluded that T. elegans can develop on the second, third and fourth instar larvae of S. zeamais. However, 19-day-old (fourth instar) S. zeamais larvae produced more T. elegans progeny with a higher female to male ratio.