A larva with an extra proleg was collected near Orangeville in southern Ontario by A. A. Harnden, of the Forest Insect Survey, on 13 August 1964. The species was Anchylopera burgessiana Zeller, a leaf folder on red oak, Quercus rubra L.

An abnormal larva reported previously (Lindquist 1964) had twin anal prolegs on a common base. The specimen reported here has a complete supernumerary proleg situated between the normal anal pair (Fig. 1). The extra appendage has 27 crotchets arranged in a complete circle. It resembles the prolegs on abdominal segments 3–6, although these bear about 42 crotchets also arranged in a circle. Crotchets on the normal anal pair of prolegs number 25 and 29.