Insect Physiology Laboratory, Section of Entomology, Department of Zoology, Aligarh Muslim University, Aligarh-202 002, Uttar Pradesh (India).
Effect of intake of food, distilled water and moistened filter paper (inert and tasteless material) on the secretion of invertase in the midgut of fifth instar larvae of Utetheisa pulchella Linn. was studied. In the starved larvae, the intake of one meal of usual food for a short duration (5 min) did not cause any appreciable increase in the secretion of invertase. The intake of several successive meals and the continuous presence of food in the midgut enhanced the invertase secretion. This suggests that continuous feeding is an important factor to stimulate the secretion of digestive enzymes. When the starved larvae consumed distilled water or moist filter paper, the midgut showed enhanced secretion of invertase. Besides the chemical stimuli by the food material (secretogogue), the physical stimuli caused by the tasteless substances are also important factors in stimulating the midgut for invertase secretion.
