# The Courtship Behavior and the Ultrastructure of Sex Pheromone Glands in the Hind Tibiae of Male Ghost Moth Endoclita davidi (Lepidoptera: Hepialidae)

## TL;DR

This study explores the courtship behavior and structure of pheromone glands in male ghost moths to understand how they communicate during mating.

## Contribution

The study identifies the hind tibiae as the site of pheromone glands in male E. davidi and describes their ultrastructure.

## Key findings

- Courtship behavior in E. davidi occurs during the scotophase and involves wing vibrations and hairpencil unfolding.
- Pheromone glands in the hind tibiae connect to scent scales via glandular ducts and microvilli.
- Glandular cells contain mitochondria, endoplasmic reticulum, and lipid droplets, indicating active pheromone production.

## Abstract

Endoclita davidi bores into and feeds on the stems and roots of Clerodendrum cyrtophyllum. The larvae, when parasitized by the fungus Ophiocordyceps xuefengensis, form valuable Xuefeng Cordyceps. To understand the mechanisms of E. davidi’s reproductive behavior, we studied its courtship behavior and sex pheromone glands. Infrared videos showed that the courtship behavior of E. davidi occurred during the scotophase, during which males vibrate their wings and unfold the hairpencils located on the hind tibiae (the third segment of the hind legs). The bottom of the pits in the bulging apical region of the hairpencils connects to the tibial glands; the epidermal cells of the hind tibiae develop into gland cells with dense microvilli. We confirmed that the male E. davidi’s pheromone glands are located in the hind tibiae and release pheromones via scent scales. Research on the ultrastructure of the sex pheromone glands in E. davidi provides a basis for further elucidating the mechanisms underlying sex pheromone release and sexual information communication.

The courtship behavior of moths is closely related to the biosynthesis and release of sex pheromones. To understand the mechanisms of the reproductive behavior of the ghost moth Endoclita davidi, a host insect of Cordyceps xuefeng (Ophiocordyceps xuefengensis), this study examined the courtship behavior and the ultrastructure of the sex pheromone gland of E. davidi. Infrared photography was used to analyze the courtship behavior, while SEM, paraffin tissue sectioning, and TEM were employed to examine the sex pheromone glands on the hind tibia. The courtship behavior of E. davidi occurs during the scotophase, during which males vibrate their wings and unfold the hairpencils located on the hind tibiae to lure the female moths. The hairpencil’s surface features regular longitudinal ridges interspersed with multiple circular pits. Multiple small holes were evident on the slightly enlarged areas close to the ends of the hairpencils. These small holes, formed at the base of the circular pits, connect to the internal glandular duct within the hairpencil, which links to the tibia glandular canal. The epidermal layer of the hind tibiae contains numerous glandular canals and dense microvilli. The glandular cells, specialized from dermal cells, contain numerous mitochondria, rough endoplasmic reticulum, clear vesicles of varying sizes, and round lipid droplets. The sex pheromone glands of male E. davidi release pheromones through the hairpencils in the hind tibia. The courtship behavior and ultrastructure of the sex pheromone gland of the male E. davidi provide a basis for further understanding pheromone release and communication mechanisms.