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Comparative morphology and distribution of antennal sensilla on Xylosandrus germanus and Xylosandrus crassiusculus (Coleoptera: Curculionidae: Scolytinae)

Christopher M. Ranger, Leona Horst, Jenny L. Barnett, Michael E. Reding, Betsy Anderson, Charles R. Krause
Annals of the entomological society of america 2016 v.110 no.2 pp. 172-188
Curculionidae, Xylosandrus crassiusculus, Xylosandrus germanus, adults, ambrosia beetles, antennae, electrophysiology, females, host preferences, hosts, insect morphology, males, orchards, plant pests, scanning electron microscopy, sensilla, smell, society, tree fruits
The non-native ambrosia beetles Xylosandrus germanus (Blandford) and Xylosandrus crassiusculus (Motschulsky) are destructive pests of plants and trees growing in ornamental nurseries and tree fruit orchards. Olfaction plays an important role in aiding female X. germanus and X. crassiusculus in locating suitable hosts; adult males of both species are flightless and not involved in host selection. Scanning electron microscopy (SEM) was used to characterize the antennae of both species, which consisted of a scape, funicle, and club. Emphasis was placed on the type, structure, and distribution of sensilla associated with the antennal clubs of female and male X. germanus and X. crassiusculus. Sensilla observed on the anterior surface of the club for females and males of both species include one type of sensillum chaeticum (SC1), one type of sensillum trichodeum (ST1), and five types of sensilla basiconica (SB1–5). The SB1 are the most abundant sensilla type found on female and male clubs for both species. Densities and distributions of these sensilla types on the antennal club are described, and possible functions are discussed based on morphology. These results provide an improved understanding of sensilla associated with X. germanus and X. crassiusculus that will aid electrophysiological investigations into their host selection behavior.