Revision of the tusked bush-crickets (Tettigonioidea: Pseudophyllinae: Dicranostomus) with description of the hitherto unknown sexes

The genus Dicranostomus belongs to the very few Orthoptera with elongated mandibular processes, here called tusks. However, it is also one of the least studied genera from whose two species only one female and two males have been known so far. We present additional material from both species and sexes that confirms that the males have the relatively longest (2–2.8 times pronotal length) tusks of all Orthoptera. Surprisingly, the females of both species differ in this character: females of D. monoceros have tusks and those of D. nitidus do not. Based on a comparison with other species, we hypothesize that the species use holes that males can defend and use to monopolize the females.