The male postabdomen of Stolotermes inopinus: a termite with unusually well-developed external genitalia (Dictyoptera : Isoptera : Stolotermitinae)

Stolotermes inopinus has large external male genitalia (phallic lobe), whic h contrast with the small genital papillae or lack of external genitalia of other Isoptera. As in the genital papilla of Mastotermes darwiniensis, a v entral sclerite pair is present, the gonopore is located ventroterminally o n the phallic lobe, and the genital area is entirely symmetrical - suggesti ng that this may be the groundplan condition of Isoptera. The relations of the phallic lobe to surrounding components like the subgenital plate, parap rocts, and certain muscles and nerves indicate that the lobe of S. inopinus is homologous with the phallomeres of other Dictyoptera. The bilateral sym metry and simple structure, however, are in strong contrast to the asymmetr y and high complexity found in male genitalia of Blattaria and Mantodea. Th e postabdominal nervous system of S. inopinus resembles that of the cockroa ch Periplaneta americana. Indications are given that the Stolotermitinae ar e related to the Kalotermitidae, Rhinotermitidae, and Termitidae rather tha n to the Termopsinae.