[The oak processionary caterpillar (Thaumetopoea processiona L.) and man: urticating apparatus and mechanism of action].

The urticating apparatus of the oak processionary caterpillar was studied by electron microscopy at times when this species was exceptionally abundant in France. Proteins of urticating hairs were studied by electrophoresis on acrylamide gel and were compared with thaumetopoein, an urticating protein of the pine processionary caterpillar, using immunological techniques. A thaumetopoein-like protein was found to be present in oak processionary urticating hairs. This protein has a histamine-releasing effect in the guinea-pig. Contact dermatitis caused by the oak processionary caterpillar is described and compared to that produced by the pine processionary caterpillar.