Leaf Size Recognition and Evaluation By Some Attelabid Weevils (3) Deporaus Sp

Abstract

Recognition of leaves by females of the leaf-rolling weevil Deporaus sp. was studied. Female weevils perform a sequence of walking along the main vein via the leaf apex (called measuring behaviour) prior to cutting. Observations of the course of walking on an asymmetric model leaf suggest that the main vein is recognized with reference to the protrusion of the leaf apex etc. A quantitative analysis of the location of cutting points indicates the following. The female weevil measures a certain length by walking along the main vein; in this way she evaluates leaf size and decides where to start cutting. An experiment utilizing a sliding leaf model revealed that it is the activity of walking itself, and not vision, that has a mensurative function. Females relate the number of eggs to be laid to the size of the apical part of the leaf, by a criterion other than leaf length (e.g. width or area). A scheme for the cutting point decision is proposed. A different set of mechanisms for measuring is used in small leaves and large leaves. The mechanism for small leaves may involve a memory of distance. The framework of leaf size recognition and the evolution of measuring behaviour are discussed, using a comparison of three species, Chonostropheus chujoi, Apoderus balteatus and Deporaus sp. (SAKURAI, 1988a, b and present paper).