a white European tussock moth with a tuft of brown hairs on the tip of the abdomen. The caterpillars have severely irritant hairs that can produce an allergic reaction, overwinter in a communal web, and can be a pest of tree foliage.
Euproctis chrysorrhoea, family Lymantriidae
brown-tail in other Oxford dictionaries
Definition of brown-tail in the US English dictionary