# Mapping Antennal Sensilla of Boxelder Bugs (Boisea trivittata) as the First Step in Understanding Overwintering Aggregation Behavior

## TL;DR

This study maps the sensory structures on boxelder bug antennae to better understand their overwintering behavior and improve pest control.

## Contribution

The first detailed mapping of antennal sensilla in boxelder bugs to study their aggregation behavior.

## Key findings

- Boxelder bugs have 20 subtypes of antennal sensilla across seven categories, with distribution varying by segment.
- Chemoreceptors for olfaction are concentrated on the distiflagellomere, while mechanoreceptors dominate closer to the head.
- Two patches of sensilla coeloconica were found on the outer lateral pedicel and basiflagellomere.

## Abstract

Insects use sensory structures called sensilla to sense the world around them, for example, to smell, detect the temperature and humidity, or position their limbs. Understanding the placement and distribution of these sensilla will enable further studies to advance prevention and control measures against insect pests. Boxelder bugs are free-living herbivores in the landscape; however, during the fall season, they exhibit behaviors to avoid adverse conditions, resulting in these insects entering buildings, such as residences, industrial structures, and commercial facilities. The majority of scent receptors on boxelder bugs are localized on their last antennal segment, with a few potential patches on the second and third segments. The majority of the receptors on segments closer to the head detect physical and mechanical changes. Knowledge of the locations of these sensory structures will enable further understanding of these insects and is necessary for studying their behaviors that result in their aggregation within structures, enabling improved methods of pest prevention and control.

Understanding the overwintering behavior of boxelder bugs (Boisea trivittata) is critical for preventing initial aggregation and secondary movement inside structures. Like many Hemiptera, boxelder bugs exhibit behaviors driven by allomones, including host cues, and field observations suggest that alarm pheromones and chemical cues mediate their end-of-season aggregation. We mapped the external morphology, ultrastructure, and distribution of the antennal sensilla of overwintering boxelder bugs via scanning electron microscopy to understand the placement of antennal sensory structures. Cuticle morphology SEM identified 20 subtypes distributed across seven categories of sensilla, namely, sensilla trichodea, sensilla basiconica, sensilla chaetica, sensilla campaniformia, sensilla coeloconica, sensilla ampullacea, and sensilla bell-mouthed, though the distribution varied considerably depending on the antennal segment. The majority of sensilla on the scape, pedicel, and basiflagellomere were mechanoreceptors, with the distiflagellomere supporting a considerable number of chemoreceptors for olfaction. However, two patches of sensilla coeloconica were located distally on the outer lateral pedicel and basiflagellomere. Mapping the number, location, and distribution of sensilla present on their antennae enables further investigations of allomone-mediated seasonal aggregation, resulting in the development of more effective pest prevention strategies against this insect.