The Nantucket pine tip moth, Rhyacionia frustrana (Scudder in Comstock) is a common pest of several southern pine species. Some tip moth research requires the sexing of pupae in order to collect emerging adults of known ages or unmated females. Characters for determining the sex of tip moth pupae were originally described in 1969. Here, we revise one of the published characters and describe seven new characters that may be used for gender determination. The new sexually dimorphic characters are: articulation of the seventh abdominal segment, dorsal spines of the second abdominal segment, length of the metathoracic tarsi, distribution of cremasteral setae, shape of the mandibular sclerite, antenna length and antenna shape.