Ultrastructure of the wing-coupling apparatus in seven Triatominae species (Hemiptera: Reduviidae) from North America.

Triatomines are the primary vectors of Trypanosoma cruzi (Chagas), the causative organism of Chagas disease, one of the most important vector-borne diseases in Mexico. Triatomine dispersal encompasses a broad spectrum of flight capacities, ranging from short-distance, low-altitude flights to active, sustained dispersal in certain species. Although recent studies have examined the phenotypic and genetic variability of flight-related traits, the specific morphological constraints hindering their aerodynamic efficiency remain poorly understood. Therefore, this study aimed to provide a comparative ultrastructural description of the wing-coupling apparatus (coaptor) in seven North American triatomine species: Triatoma bassolsae (Alejandre et al.), T. picturata (Usinger), T. pallidipennis (Stål), T. longipennis (Usinger), T. rubida (Uhler), T. mazzottii (Usinger), and Paratriatoma lecticularia (Stål). Using light and scanning electron microscopy (SEM), the topography of the ctenidia, the mechanical gap, and imbricated scale-like structures were characterized. The results revealed a consistent tripartite morphological pattern across all species; however, all the species exhibited a central morphological discontinuity separating the ctenidium from the posterior rugose prominence. Ctenidial bristle count showed interspecific variation, ranging from 16 visible bristles in T. rubida to 33 in T. bassolsae. These counts corresponded to the anterior row of the ctenidium captured in SEM micrographs at 500× magnification. These findings provide high-resolution diagnostic cuticular characters for species differentiation and led to the hypothesis that a structural discontinuity along the hemelytron margin may influence functional wing coupling. This study highlights the importance of ultrastructural analysis in providing high-resolution diagnostic traits to complement traditional taxonomy and understanding Triatominae functional morphology.