• S S Krishna

      Articles written in Proceedings – Animal Sciences

    • A behavioural assessment of the impact of some environmental and physiological factors on the reproductive potential ofCorcyra cephalonica (Stainton) (Lepidoptera: Pyralidae)

      S S Krishna S N Mishra

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      Results of a study of certain specific environmental and physiological variables affecting the reproductive activity (specially egg yield and egg hatchability characteristics) ofCorcyra cephalonica (Stainton) (a pyralid pest damaging a variety of stored edible commodities) are considered, from a behavioural point of view, in this contribution. The environmental cues examined are (a) light, (b) population density, (c) space availability and (d) host presence. The physiological factors tested are (a) age, (b) sex ratio, (c) nutrition and (d) time of mating. The findings obtained in this investigation provide a basis to comprehend more meaningfully the complex, delicate and varied effects produced by these factors on the reproductive performance of this moth in relation to its establishment on jowar, one of the stored products naturally infested by this pest.

    • Variation in the reproductive capacity ofEarias vittella (F.) (Lepidoptera: Noctuidae) following antennectomy or alactomy in males or wing loss in both sexes

      P H Pathak S S Krishna

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      An extremely low egg output, almost approaching zero level, and with no sign of viability, occur inEarias vittella (F.) when the females are coupled for mating with antennectomised males or if both sexes paired for coition are wingless. However, sexual union arranged between normal females and males whose both wings or only fore or hindwings are excised facilitates these insects to deposit fertile eggs whose number, however, always remains markedly lower (more so when the males in the breeding pairs are without hindwings) in comparison to that recorded for mated females in pairs where both sexes are normal.

    • Effect of certain experimental regimens on mating behaviour and the impact of nutritional difference between copulating males and females on the reproductive programming inDysdercus koenigii (Fabr.) (Heteroptera: Pyrrhocoridae)

      K P Shahi S S Krishna

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      Male/female individuals of the red cotton bug,Dysdercus koenigii (Fabr.) in a given population, when provided equal mating opportunities, exhibit interesting variability in their mating trends with more coitions occurring between sexes comprising 3- and 5-day old adults. Mating between females ingesting cotton leaf and cotton seed-fed males is a futile sexual exercise in this bug’s reproductive programme yielding no output of fertile eggs. However, in a vice versa situation, the mateds deposit viable eggs the proportion of which, following a second mating with seed-fed males, gets appreciably augmented in the subsequent egg batch.

    • Nutritional modulation of reproduction in two phytophagous insect pests

      S S Krishna

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      InEarias vittella (F.) (a major noctuid pest of malvaceous crops) changes in the larval food quality (developing seeds, mesocarp, epicarp of okra fruit or the entire fruit; ovary of shoeflower) in either or both sexes led to pronounced disparities in the reproductive performance of the emerging moths. Highest breeding potential was observed when males and females obtained their nourishment, during postembryonic period, from developing seeds of okra of 0–8 days old and such nutrition must be made available for the caterpillars at least for the first 3 days of their lives to attain enhanced level of reproductive efficiency later as moths. During adult life, a carbohydrate nutrient was mandatory for these mated females to realize full fecundity which got tremendously boosted when the sugar was raffinose.

      Appreciable increase in ovarian weight with marked improvement in oviposition occurred inTribolium castaneum (Herbst) (a serious tenebrionid pest of cereals and other plant-derived stored commodities) when both larvae and adults ate whole flour instead of semolina, both enriched with yeast. This became further augmented when the flour ingested by these beetles during adult life was previously extracted in 100% ethanol and then reinforced with yeast. However, whole wheat flour or yeast alone given as food to such reared adults caused a sharp fall in the egg deposition of females. Number of eggs laid by mated females also differed considerably when their imaginal diet consisted of one of certain selected nutrients, oilseeds or spices—all supplemented with yeast. Egg hatchability was always 100%.

    • Digestive physiology and food utilization of the larvae ofEarias vittella (Lepidoptera: Noctuidae) from its malvaceous host plant

      S S Krishna

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      The hydrogen-ion concentration of the contents of fore-, mid- and hindgut of the larva ofEarias vittella (F.) lays within a pH range of 8-8 and 9-6 These caterpillars possessed the ability to break down starch, raffmose, maltose, melibiose, sucrose and proteins. Synthesis of certain higher oligosaccharides indicating transglycosidic activity was also noticed during hydrolysis of raffinose, melibiose and sucrose inin vitro experiments. The activity of carbohydrases detected in the larval midgut was variably influenced by the hydrogen-ion concentration of the medium. Further, they differed from one another in their relative strength. Amylase was the most powerful and a-galactosidase was the weakest of all. An in vivo examination into the fate of fed starch, maltose, cellobiose and lactose within the gut revealed the physiological competency of the caterpillar to utilise only the first two carbohydrates (the former partly and the latter completely) through swiftly operating processes of digestion and absorption.

      Movement of ingested food through the gut of the caterpillar was a rapid process. The first lot of food residue passed out of the hindgut within a mean time of 103 min after feeding. However, the entire alimentary canal got cleared of the ingested food only 36 h after a meal.

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