Morphology and Distribution of the Antennal Sensillia of the Leaf Beetle, Ambrostoma quadriimpressum (Coleoptera: Chrysomelidae)

Abstract

The leaf beetle, Ambrostoma quadriimpressum Motschulsky (Coleoptera: Chrysomelidae) is the predominant pest of elms (Rosales: Ulmaceae) in China, Russia, and elsewhere in northesatern Asia, where it feeds on buds and leaves of several elm trees (Ulmaceae) and inhibits elm trees sprouting, severely affects elm trees growth and eventually leads to mortality. The present study aimed to elucidate the insect-plant and insect-insect chemical communication mechanisms involved with this process by observing the antennae and sensilla of A. quadriimpressum using scanning electron microscopy. The filiform antennae of both sexes of the both species consist of the scape, pedicel, and nine flagellomeres. Based on their morphology, 3 types of sensilla chaetica, 2 type of sensilla trichodea, 2 types of sensilla basiconica and Bohm bristles were distinguished on the antennae in both sexes. No sexual dimorphism was observed in the distribution and types of sensilla. SC1, ST1 and ST2 are distributed throughout the antennae. SB1 and SB2 are absent from the scape, pedicel and the first 3 flagellum. SC2 and SC3 are located on the antennal flagellum. BB only occur on the scape and pedicel. ST1 and ST2 are more abundant than the other types of sensilla on the antennae. The distal antennal sensilla of A. quadriimpressum had notably more sensilla than proximal ones in type and number, indicating this is the main area to detect environmental stimuli for feeding or oviposition The putative functions of other sensilla types were also discussed with reference to their morphology, distribution, and ultrastructure.