The Cercal Sensilla of the Praying Mantis Hierodula patellifera and Statilia maculata: A New Partition Based on the Cerci Ultrastructure

Cerci function as crucial sensory organs in insects, featuring a diverse array of sensilla on their surface, analogous to those found on antennae. Using scanning electron microscopy (SEM), we characterized the ultrastructure and distribution of cercal sensilla in <i>Hierodula patellifera</i> (<i>H. patellifera</i>) and <i>Statilia maculata</i> (<i>S. maculata</i>). Results show that the cerci of <i>H. patellifera</i> and <i>S. maculata</i> are highly similar, with main differences observed in the number of cercal articles and the length of cerci. The cerci of both species and sexes are composed of multiple cylindrical articles, and there is variation in the number of types of sensilla on their surface articles within sex and individuals. Females possess more cercal articles than males, and their cerci are generally longer than those of males. In both sexes of these praying mantises, four types of cercal sensilla were identified: sensilla filiformia (Sf), sensilla chaetica (Sc), sensilla campaniformia (Sca) and cuticular pore (CP), with sensilla chaetica further classified into two subtypes (ScI, ScII). Sc are widely distributed over the entire cerci, while Sf are distributed in a circular pattern on the cercal articles. While the overall distribution patterns of cercal sensilla were conserved between the sexes, significant sexual dimorphism was observed in the morphological parameters of the sensory hairs, including their quantity, length, and basal diameter. Based on distinct sensilla arrangements on the cerci, we propose a novel zoning of the cerci into four parts (I-IV), which reflects a functional gradient specialized for reproductive roles: the proximal region is enriched with robust mechanoreceptors likely involved in mating and oviposition, the central region serves as a multimodal hub for integrating courtship and mating cues, and the distal region is simplified for close-range substrate assessment. These findings highlight the adaptive evolution of cercal sensilla in relation to reproductive behaviors and provide a morphological basis for future studies on mantis phylogeny and sensory ecology.