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

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