Feeding behavioural patterns of Imbrassia belina larvae that minimizes the production of tannins in Colophospermum mopane leaves

Abstract

Mopane (Colophospermum mopane) trees respond to herbivory by producing secondary metabolites known as tannins. In order to exploit such trees, insects will adopt feeding patterns that will best reduce production of such feeding deterrents. To elucidate this, the behavioural feeding patterns of Imbrasia belina larvae were studied on Mopane trees and artificial damage on the same was done by punching small holes on a large number of leaves over a period of 25 days. Similarly, a control was used to simulate feeding behaviour of I. belina larvae by removing a large number of full leaves on each day over a period of 25 days. In each instance leaves were collected and tested for tannin content using the Folin-Ciocalteau method. The feeding behavioural patterns showed that I. belina larvae will feed on a full leaf at a time and will not leave a leaf unfinished. The surface area of leaf eaten by these larvae increases exponentially from the first instar to the last instar until the entire tree foliage is finished. The results obtained for tannin content showed that removing full leaves as in the control resulted in no increase in amount of tannin produced whereas artificial damage resulted in an increase in amount of tannin produced. From these results it can then be concluded that the feeding behaviour of I. belina will minimises production of tannins on Mopane trees.