Leaf trenching by Indian red admiral caterpillars for feeding and shelter construction

Abstract

AbstractMany folivorous insects sever leaf veins, trench across leaf blades, or girdle petioles prior to feeding on leaves. The purpose of these behaviours is generally thought to be sabotage of the anti‐herbivore chemical defences of host plants. For insects that construct leaf shelters, these behaviours may make leaves easier to roll or fold. Larvae of the Indian red admiral butterfly, Vanessa indica (Herbst), cut trenches at the base of host plant leaves and construct leaf‐fold shelters. I attempted to determine which of the above functions the trenching behaviour of V. indica larvae serves. If the function of trenching is to facilitate leaf‐folding, then larvae should cut trenches before folding leaves. When the larvae used larger leaves, they tended to trench them prior to folding them. This suggests that the function of trenching behaviour is to make leaves easier to fold. However, larvae sometimes cut trenches after folding the leaves, suggesting that this behaviour has additional functions. When the larvae were about to moult or pupate, they did not cut trenches, suggesting that trenching behaviour may also be involved in feeding.