LEAF SIZE SELECTION BY INSECTS - A PHENOMENON CREATED BY RANDOM SAMPLING

Using random sampling as a simple method to collect leaves in a tree crown we have found in weewil Polydrusus ruficornis feeding on Betula pubescens ssp. tortuosa a clear preference for small leaves. The leaf beetle Gonioctena Pallidus feeding on Salix phylicifolia was shown to prefer large leaves. Both these species tend to feed on young tip leaves of long shoots but leaf size in birch decreases from shoot base to its tip while that in willow increases. These regular patterns of variability of leaf size within a long shoot lead to the opposite trends in ''leaf size selection'' in Polydrusus and Gonioctena. Using leaves of the same age (brachyblast leaves) in birth we have destroyed the phenomenon of ''leaf size selection'' in weewils. A special procedure of non-random sampling is offered to find the real insect preference to a certain leaf size.