Antennal sensilla of Eucryptorrhynchus chinensis (Olivier) and Eucryptorrhynchus brandti (Harold) (Coleoptera: Curculionidae).

Eucryptorrhynchus chinensis (Olivier) (Coleoptera: Curculionidae) and E. brandti (Harold) (Coleoptera: Curculionidae) are the two most important pests of tree-of-heaven, Ailanthus altissima (Mill.) Swingle and its variety Ailanthus altissima var. Qiantouchun in China. They are also considered potential biological control agents for tree-of-heaven in North America. In this study, the external morphologies and antennal sensilla of both species were examined using scanning electron microscopy to better understand their host-finding mechanisms. Eleven morphological sensilla types were recorded, that is, Böhm bristles, six types of sensilla chaetica (Sch. 1-6), two types of sensilla basiconica (Sb. 1-2), and two types of sensilla trichodea (St. 1-2). Sch. 5 were absent from the antennae of E. chinensis, while Sch. 2 were absent from the antennae of E. brandti. Abundant cuticular pores were present on the antennae of both species. Three types of sensilla on the antennae of E. chinensis that were not found in a previous study, and ten different types of sensilla on the antennae of E. brandti were identified for the first time. The possible functions of the sensilla types are discussed based on a comparison with previous studies. Four types of sensilla (Sb. 1, Sb. 2, St. 2, and Sch. 6) on the antennae of both species indicate chemoreception may play a significant role in host location.