Sexually dimorphic antennal structures of New Zealand Cave Wētā (Orthoptera: Rhaphidophoridae).

Insect antennae carry diverse sensory organs for detecting information about their environments and facilitating interaction among individuals, particularly for reproductive behaviour. As such they are predicted to be sexually dimorphic, especially in species which do not use visual or auditory mate-location. The cave wētā are such animals, suggesting that they rely heavily on chemical and tactile information to interact. Sensilla morphology and sexual dimorphism was investigated in two species; Pachyrhamma acanthocera and P. waitomoensis, using scanning electron microscopy. Fourteen types of sensilla basiconica, campaniformia, chaetica, coeloconica, trichodea and Böhm's sensilla were identified. Among these, sexual dimorphism in the length of four subtypes was detected, and surprisingly, P. waitomoensis males completely lacked all but two of the porous sensilla types. In addition, three types of unique horn-like and hooked antennal protrusions in male P. acanthocera are described, along with similar, but less diverse structures on the antennae of male P. waitomoensis. [ABSTRACT FROM AUTHOR]