Studies on the Choice of Food-plant and certain Aspects of the Digestive Physiology of the Larvae and Adults ofAthalia lugens proxima(Klug) andEpilachna vigintioctopunctata(F.)

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Abstract
Athalia lugens subsp. proximo (Klug) is a pest of cruciferous crops, and shows special preference for turnip. In the matter of selection of food, smell and taste of the food and the age of the plant are important factors. Epilachna vigintioctopunctata (F.) is a pest of solanaceous plants, particularly brinjal. In this insect only smell and taste are important factors in the selection of food.The hydrogen-ion concentrations of the salivary gland, foregut, midgut and hindgut of the larva of Athalia are 6·4–6·6, 6·4–6·8, 6·6–6·8 and 7·0 and of the adults 6·2–6·4, 6·4–6·6, 6·4–6·6 and 6·6, respectively. The hydrogen-ion concentration of the salivary gland, foregut, midgut and hindgut of the larvae of Epilachna are 5·4, 6·4–6·8, 6·0 and 6·0 and of the adult 6·6–6·8, 6·2, 6·0 and 5·4–5·7, respectively.The foregut and hindgut of the larvae and adults of Athalia and Epilachna do not secrete enzymes; the salivary glands of both larva and adult of Athalia secrete amylase, the midgut epithelium of both larva and adult of Athalia secretes amylase, maltase, invertase, lactase, lipase and protease. The salivary glands of the larva of Epilachna secrete amylase, but those of the adult do not, and the midgut epithelium of both larva and adult secretes amylase, maltase, invertase, lactase and protease. The midgut of both larva and adult of Epilachna secretes lipase also, although in the adult no more than traces are detectable. The proteases in both insects act in slightly acidic media.

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