Scanning Electron Microscopic Analysis of Antennal Sensilla and Tissue-Expression Profiles of Chemosensory Protein Genes in Ophraella communa (Coleoptera: Chrysomelidae)

Functional morphology of antennae and sensilla of the fungivore beetle, Triplax ainonia Lewis (Coleoptera: Erotylidae)

The antennal sensilla play an important role in many behavioral activities of insects. The fungivorous beetle Triplax ainonia Lewis (Erotylidae) is an important pest which prefers to feed on Pleurotus mushrooms. In order to clarify the types, number, and distribution of the antennal sensilla of male and female T. ainonia, scanning electron microscopy was used. The results showed that there were five sensillum types on the antennae of adults male and female, including Böhm's bristles (BB), sensilla chaetica (three subtypes: SC 1, SC 2, and SC 3), sensilla basiconica (three subtypes: SB 1, SB 2, and SB 3), sensilla trichodea (ST), and sensilla styloconica (SS). Among all the sensilla, the number of SB 2 was the most abundant in both sexes. We found that there was no sexually dimorphic in the sensillum types, but there were differences in the number, lengths, and diameters of some sensilla between males and females. Based on the information of the morphology and distribution of the sensilla, the potential functions of the antennal sensilla of T. ainonia adults were discussed. The results of this study provide a basis for further study on the behavioral ecology and electrophysiology of the fungivore beetles of the Erotylidae.

Morphology and location of sensilla in the antennae and ovipositor of Sirex noctilio (Hymenoptera: Siricidae)

The woodwasp Sirex noctilio Fabricius is a major quarantine pest that was reported in China in 2013 and mostly damages Pinus sylvestris var. mongolica. Reverse chemical ecology, which uses chemical lures to catch or block insects from mating is the classic way to control forestry pests. This indicates that insect sensilla play a crucial role in detecting external chemical and physical stimuli. Nonetheless, the categorization and distribution of sensilla on the antennae and ovipositor of S. noctilio are insufficiently specific. In this paper, scanning electron microscopy (SEM) was used to observe the ultrastructure of the sensilla of S. noctilio on the antenna and ovipositor. It was found that the types and distribution of sensilla on the antennae of S. noctilio male and female are consistent, and six types of sensilla are found: sensilla trichodea (ST), sensilla chaetica (SC), Böhm bristles (BB), sensilla basiconica (SB), sensilla ampullacea (SA), and contact chemoreceptors (CC). Besides, there are five types of sensilla on the female ovipositor. In addition to ST, SC and BB, two more types of sensilla are also found: sensilla cavity (SCa) and sensilla coeloconica (SCo). Through identification of the morphology and distribution of the sensilla, the functions of different sensilla in the mating and host selection mechanisms of S. noctilio are proposed, thereby establishing a foundation for S. noctilio chemical communication research.