Morphogenesis and functional adaptation of grasping leg structures in Distirogaster tuberculifera Horváth, 1914 (Insecta: Heteroptera: Reduviidae)

The fossula spongiosa, a specialized grasping structure located on the legs of assassin bugs (Heteroptera: Reduviidae), plays a key role in prey capture, and substrate adhesion. In this study, we investigate the morphogenesis and functional adaptation of the fossula spongiosa in Distirogaster tuberculifera Horváth, 1914 (Heteroptera: Reduviidae: Ectrichodiinae), based on a unique set of specimens representing all five juvenile developmental stages, the only known material worldwide, preserved at MNHN Paris. Using a combination of light microscopy, scanning electron microscopy (SEM), and morphometric analyses, we describe structural changes across successive nymphal instars and the adult stage. Our results reveal distinct morphological transformations, including the formation of microtrichia patterns, cuticular modifications, and the gradual specialization of the fossula spongiosa as a highly specialized grasping apparatus. Functional implications of these changes are discussed in relation to predatory behaviour, ecological adaptation, and potential bioinspired applications in surface adhesion. This study provides new insights into the evolutionary significance of grasping leg structures in Reduviidae and highlights their relevance for applied sciences.