The first instar of Matus ovatus Leech is described and illustrated. The analysis of the primary chaetotaxy of legs, head, and last abdominal segment of M. ovatus revealed no significant differences between this species and the previously described M. bicarinatus. Undescribed primary anatomical features of the tribe Matini presented herein include (1) a tentative identification of anterior tentorial pits and fragments of the anterior tentorial arms, (2) anterior protergal modifications and chaetotaxy, and (3) complete sclerotization of the seventh abdominal segment. Differences in mandibular morphology permit identification of first instars of M. ovatus and M. bicarinatus in the eastern United States.