On Dec. 14, 1890, I secured from the upper Piney Branch region (District of Columbia) a small quantity of swine dung that had been dropped in the edge of open woods, and seemed to be old enough to contain with probability larvæ or puparia of Diptera. This was placed in a large glass jar, with a few inches of sand in the bottom, occasionally moistened and kept in a moderately cool room in the house. The dung was soon noticed to be full of larvæ which in a short time crawled out of it entirely, cluseterd on the inside of the glass, or worked themselves down into the sand, manifesting a considerable migratory instinct, no doubt induced by the moisture and mild tempearture.