Ultrastructural characterization of sensilla and sexual dimorphism in the antennae of Eueides isabella dianasa (Hübner, 1806) (Lepidoptera: Nymphalidae: Heliconiinae)

Abstract To better understand the communication mechanisms involved in the search for host plants and the location of sexual partners, this study aimed to identify the presence of sexual dimorphism in the external morphology, distribution, and typology of the antennal sensilla of male and female Eueides isabella dianasa (Hübner, 1806) (Lepidoptera: Nymphalidae) using Scanning Electron Microscopy (SEM). Six individuals (three males and three females) were analysed. Observations revealed that the species exhibits sexual dimorphism, with claviform antennae displaying evident external morphological differences between the sexes. Five types of sensilla were identified: Sensilla basiconica (SBa), sensilla coeloconica (SCo), sensilla chaetica (SC), sensilla trichodea (STr) and sensilla squamiformia (SSq). Morphometric analysis revealed significant differences in the length and width of some sensilla between males and females, suggesting the presence of functional sexual dimorphism, particularly in the length variations of SC I, SC III, Ssq I, and STr III, as well as in the width of SC III and STr III. The results contribute to the knowledge of the types of sensilla in E. i. dianasa , as well as to the understanding of the sensory system of butterflies, particularly those of the genus Eueides .