Sexual dimorphism of antenna of the scale insect Drosicha corpulenta (Kuwana) (Hemiptera: Coccoidae: Monophlebidae)

Abstract The scale insect Drosicha corpulenta is a serious pest of various garden trees. A comprehensive knowledge of the insect olfactory system is essential for the design and implementation of efficient semiochemical-based control strategies. Antennae are the primary olfactory organs in insect. To date, the antenna features of D. corpulenta have not been investigated in great detail. In this study, we used scanning electron microscopy to investigate the antennal morphology and sensilla distribution of both sexes of D. corpulenta in detail. The antenna of D. corpulenta exhibit obvious sexual dimorphism: antennae of the male are markedly longer than those of the female. Furthermore, each male flagellomere consists of three globular nodes, in female, however, the flagellomeres one to three are cylindrical, and the following flagellomeres exhibit an asymmetrical swelling at the distal parts except the last flagellomere which is dumbbell-shaped with distal narrowly. Seven types of sensilla were found on the antennae, including three types of sensilla trichodea (ST1, ST2, ST3), three types of sensilla chaetica (SC1, SC2, SC3), and sensilla basiconica (SB). Remarkable sex dimorphism in the sensilla composition of D. corpulenta was also observed. Major differences between the both sexes were found in the type, distribution, number and size of the identified sensilla. We also discuss on the possible functions of these sensilla based on their characteristics. The results of this study provide an important foundation for the studies that link morphological characteristics to insect behavior and should stimulate the development of efficient semiochemial-based control strategies against D. corpulenta.