On July 12, 1950 a collection of adults of the moth Acentropus niveus (Oliv.) was made on the north shore of Lake Erie near the village of South Cayuga, Ontario (Maps A, B-3). At the southern limits of the townships of Dunn and South Cayuga (Haldimand County) a shallow bay extends for a distance of about two miles along the shore of the lake (Map A). Along this bay is a sandy or gravelly beach ten to twenty yards wide backed by a cliff of clay that rises abruptly above the beach. On the day the collections were made the sky was clear and a brisk southerly breeze was causing waves to wash on the beach. The action of the waves had deposited debris, consisting largely of tangled masses of a filamentous green alga and exuviae of the mayfly Hexagenia occulta, in a windrow six inches to two feet wide along the shore. The moths ere found in this debris, most of them lying dead and with bedraggled wings, while some lay on their backs with wings stuck to the damp surface and with legs kicking and a few were crawling about on the debris.