The effects of photoperiod on some aspects of the biology of Oryzaephilus mercator (Fauvel) (Coleoptera: Silvanidae)

The effects of three photoperiod regimes (24LL, 24DD, LD 12:12) on the duration of the developmental, pre-oviposition and oviposition periods, etc. in Oryzaephilus mercator were investigated under fluctuating laboratory conditions (25.9-30.2 degree C and 75.4-85.3% r.h.) on Irvingia gabonensis var. excelsa (African mango), Citrullus lanatus (melon) and Arachis hypogaea (groundnut). The mean egg period was longest in the LD 12:12 regime; the larval and egg-adult periods were shortest in this regime. The egg-adult developmental period was longest in the 24LL regime. Differences in the duration of these developmental stages among the regimes were significant. The mean egg, larval and pupal mortalities were highest in the LD 12:12 regime and lowest in the 24LL regime. The pre-oviposition period was longest in the LD 12:12 regime on all oilseeds; using indices of the number of mean total eggs produced per female and duration of oviposition period, this was also the most ideal regime.