The eggs of the stored grain pests, Tribolium castaneum (Herbst), T. confusum (Duval) (Coleoptera: Tenebrionidae) and Cadra cautella (Walker) (Lepidoptera; Pyralidae) belonging to three age groups, 1, 2, and 3 days-old, were exposed to ultraviolet (UV) radiation with 254nm wavelength (UV-C) for different durations to determine irradiation effects on egg-hatching and adult emergence. An increase in time of exposure to UV-rays caused a gradual decrease in the percentage of hatching of eggs in all age groups of eggs. No hatching occurred after 24 minutes of exposure in 2 and 3 day-old eggs of T. confusum. C. cautella eggs were less sensitive to UV-rays than were T. castaneum and T. confusum eggs. All the exposure periods significantly reduced the eclosion of adults in all the experimental insects. No adults emerged when 3 day-old eggs of T. castaneum were irradiated for 16 or 24 minutes, or from 2 and 3 day-old eggs T. confusum irradiated for 16 or 24 minutes.

No abstract

The efficacy of different concentrations of the commercial neem-based insecticide, Nimbicidine® was evaluated against the eggs of the red flour beetle Tribolium castaneum (Herbst). The insecticide significantly inhibited the hatching, pupation and adult emergence of the beetle. The latent effects of Nimbicidine® on the next generation progenies were expressed by significant reductions in the growth of larvae, pupation and adult emergence coupled with lengthened developmental period, but the sex ratio was unaffected. Key words: Tribolium castaneum, Azadirachtin, hatching, pupation, adult emergence, growth and development, sex ratio Univ. j. zool. Rajshahi Univ. Vol.25 2006 p.51-55

Ecdysone is a steroid hormone especially found in insects and mammals. One day old pupae of Tribolium castaneum were exposed to crude ecdysone at different concentrations of 10, 20, 40, 80, 160, and 320 µl/kg of whole wheat flour each for 1, 3 and 5 days. Adult recovery was significantly reduced in the treated pupae (F=3.47, P<0.01, df=7), and produced deformed individuals (F=39.29, P<0.001, df=7) at all exposure periods. The developmental time was similar in both the treated and untreated ones. The latent effect of the ecdysone treatment increased both the larval (F=4.26, P<0.001, df=7) and pupal (F=8.56, P<0.001, df=7) periods of the progeny reared on untreated foods. Similarly, the latent effect hampered recovery of the adult progeny (F=7.79, P<0.001, df=7) producing deformed individuals (F=2.65, P<0.05, df=7).

Five-day old larvae of the susceptible (FSS-II) and organophosphorus-resistant (PH-I) strains of the red flour beetle Tribolium castaneum were exposed under laboratory conditions to food treated with 100, 250, 500 and 1000 ppm of a synthetic pyrethroid Fenvalerate up to adult emergence. The larval mortality was assessed at 1-, 3-, 7-and 15-days post-exposure, and up to pupation. PH-I was found less susceptible to Fenvalerate than FSS-II which required 1.2 to 3.1 fold more insecticide to induce 50% mortality. The pyrethroid treatments significantly increased the larval and pupal periods (P<0⋅05) in both the strains and the formation of pupal and adult progenies was adversely affected (P<0⋅001).