Scanning electron microscopy analysis of the antennal sensilla in the rare saproxylic beetle Elater ferrugineus (Coleoptera: Elateridae)

Abstract

This work provides the first morphological analysis (both at gross and fine level) of the antennal structures in the genus Elater (Coleoptera, Elateridae). The typology, number and distribution patterns of the antennal sensilla in the rare saproxylic Elater ferrugineus (both male and female) were studied using scanning electron microscopy (SEM). The serrate antennae of E. ferrugineus consisted of a scape, a pedicel, and nine flattened flagellomeres. Overall, 10 types of sensilla were identified according to their morphological features: one type of sensilla chaetica (Ch), one type of Böhm sensilla (Bo), three types of sensilla trichodea (Tr.1–3), two types of sensilla basiconica (Ba.1–2), one type of sensilla styloconica (St), one type of grooved peg sensilla (Gp) and one type of sensilla campaniformia (Ca). A marked sexual dimorphism was found at both gross and fine scale. The male antenna was bigger (8.6 mm) than the female one (7.0 mm) and carried one type of sensilla trichodea (Tr.2) absent in female antennae possibly responsible for reception of the female-emitted sex pheromone. The female antenna carried a higher number of sensilla (~ 9800) than the male one did (~7,000), with more abundant sensilla chaetica (Ch) and basiconica (Ba.1 and Ba.2).