Athalia spinarum. Turnip Saw-fly, known popularly as the Black-caterpillar, Black-canker, Black-palmer, Negro, etc.

Mr. Curtis observes, that "As early as May, or sooner, the Saw-flies make their appearance; the female lays her eggs on the under surface along the margin of the leaf. These hatch in about five days, and produce the Negroes, which are not thicker than a fine thread, and white, but after changing their skins, they become black, and eventually are three-quarters of an inch long, when they are more of a lead colour and yellowish-white beneath their skins, being very much wrinkled; they erect their tails whilst feeding, and are stretched out at full length in repose, or lie sleeping coiled up on the leaf; they are feeding about three weeks, after which they descend to the ground, and enter the earth, where they form a cocoon, silvery inside, in which the larva eventually becomes a pupa. In summer they remain only three weeks in this quiescent state, but the autumnal ones lie buried through the winter." - Gard. Chron. Hand-picking is the only mode of removing the caterpillars.