• M R Delvi

      Articles written in Proceedings – Animal Sciences

    • Ecological energetics of the grasshopperPoecilocerus pictus in Bangalore fields

      M R Delvi T J Pandian

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      The structure and biomass ofPoecilocerus pictus population in four fields in Bangalore were estimated by direct observation method. Results on the density ofP. pictus, the survivorship curve of the grasshopper and the growth of the population are reported.

      The data on feeding rates, assimilation and conversion obtained in the laboratory were applied to the size and structure of theP. pictus populations in the different fields to estimate the rate and efficiency of energy flow through the population. The results indicate the defensive mechanism developed by the plant against predation. Efficiencies of exploitation, assimilation and production by the populations averaged 3·4, 34 and 15% respectively. Factors like predation, food and space do not appear to regulate the size of the population. Probably it is controlled by intrinsic population factors.

    • Dietary water balance in a tropical insect

      M R Delvi

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      Dietary water intake of the tropical grasshopperPoecilocerus pictus fedad libitum from hatching to death on the milkweedCalotropis gigantea averaged 85 or 51 g at 26°C and 171 or 78 g at 36°C for a female and male respectively. As much as 54 or 96 g dietary water is lost via faeces by a female at 26 or 36°C; the corresponding values for a male was 37.5 and 36.2 g. A male or female carried at death about 9 or 6% of the respective dietary water absorbed at 26 or 36.°C. Water loss via exuvia amounted to 26 mg in all the series. Due to oviposition 4.8 or 7.4% of the total water absorbed was lost by a female at 26 or 36°C. There exist a very close relationship between the efficiencies of matter assimilation and water absorption. The high dietary water intake and absorption rates reported for the tropical lepidopteranDanaus chrysippus are correlated with the accumulation of water to meet the requirements during the nonfeeding pupal stage.

    • Effects of insecticide, permethrin, on dietary water utilization in eri-silkwormPhilosamia ricini

      Prakash R Naik M R Delvi

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      Dietary water intake in Eri-silkwormPhilosamia ricini fedad libitum castor leafRicinus communis from hatching to pupation at 26±2°C averaged 16174 mg/insect. As much as 3966 mg of dietary water is lostvia faeces and 65% of the absorbed water is lost through transpiration retaining only 35% in the body. Rates of water intake, absorption, lossvia faeces and transpiration decrease from the Ist instar to Vth instar larvae and are correlated to the increasing body weight and/or age. Water intake inP. Ricini fed permethrin, a pyrethroid insecticide, treated leafR. Communis averaged 8649 mg/insect which is about 50% less than the normal intake. Water utilization in the insecticide fedP. Ricini is considerably less than the normal. It is suggested, the mechanism by which insecticide inhibit the utilization of water could be through, repellency, disruption of feeding physiology and other chronic toxicity possibly related to insecticide action.

    • Effect of leaf ration on dietary water budget of the larvae of silkwormBombyx mori and eri silkwormPhilosamia ricini

      M R Delvi P G Radhakrishna Noor Pasha

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      Dietary water intake in penultimate two instars of silkwormBombyx mori and eri silkwormPhilosamia ricini fedad libitum on mulberry leafMorus alba and castor leafRicinus communis respectively at 26±2°C is reported. The lower ration level results in accumulation of water content in the body of insects. The water retention efficiency (per cent of absorbed water retained in the body) increases with the decreasing ration level. The larva retains higher amount of water in the body by increasing water retention efficiency from 22% at 100% ration to 61% at 25% ration. This is an important adaptive mechanism exhibited by larvae. The water utilization budgets are discussed with the budgets available for other insects.

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