Craighead (1923) described the larvae of four North American species of Acunthocinus and constructed a key for their separation; two of these, A. nodosus (Fab.) and A. obsoletus (Oliv.), occur in the eastern half of the continent. During recent studies of cerambycids infesting fire-killed pine in central Ontario, another species, A. pusillus Kby., was encountered in large numbers, but the larvae could not be identified because of the lack of a published larval description. Larvae were eventually reared from known parent adults, and, since wood-boring Coleoptera are most frequently encountered in immature stages, the following description has been prepared.