Sensory Morphology of <i>Geodorcus helmsi</i> (Coleoptera: Lucanidae) and its Relevance to the Conservation of New Zealand Stag Beetles

Insects use sensilla to detect chemical and physical stimuli, mediating behaviours such as mate finding, foraging and mechanosensory responses. The distribution and density of sensilla can be examined using scanning electron microscopy. Investigating these structures can help elucidate rarely observed behaviours (e.g. mate finding and foraging). The mating behaviour of the Geodorcus stag beetles of New Zealand is not well understood, as most species (eight of ten) are listed as ‘threatened’, ‘at risk’ or ‘data deficient’ under the New Zealand Threat Classification System. We examined the most common species of Geodorcus , G. helmsi , and compared sensilla on the maxillary palps, antennae and legs of males and females. Male antennae were more densely packed with sensilla and had sensilla campaniformia, absent in females. Additionally, male antennae were larger than those of females, scaling proportionally with body size, suggesting that males have greater sensory capacity and are likely attracted to a pheromone the females emit. Our study sheds new insight into the sensory biology, mating behaviour and life history of G. helmsi . More broadly, it contributes to understanding the reproductive ecology of Geodorcus . Understanding how these beetles interact and locate mates can inform conservation management, for example, by guiding captive breeding programmes and pheromone‐based monitoring strategies for threatened Geodorcus species.