Larval Dispersion and Survivorship in a Leaf-Mining Moth

We observed and quantified leaf miner distribution on Quercus geminata in order to determine its relation to leaf abscission and the effects of leaf abscission on larvae. A leaf-mining moth, Stilbosis quadricustatella, exhibited a clumped distribution of mines among leaves of the evergreen oak Quercus geminata. Mines tended to be on large, peripheral, and undamaged leaves so that leaves were often multiply minded. Mined leaves, especially those with multiple mines, tended to abscise early. Unless miners in an abscised leaf were very near to pupation, abscission killed them. Premature leaf fall was by far the largest source of larval mortality for this moth. A preliminary analysis suggested that the clumping of miners was no more favorable to the tree (in terms of number of leaves abscised early) than to the insect.