# Antennal Sensilla Basiconica Responses to Pheromones and General Odorants in Red Imported Fire Ants, Solenopsis invicta

## TL;DR

This study explores how red imported fire ants detect different smells using their antennae, revealing differences in odor sensitivity between worker ants and winged females.

## Contribution

The first comprehensive mapping of basiconica sensilla responses to general odorants in red imported fire ant castes.

## Key findings

- Basiconica sensilla on fire ant antennae show broad sensitivity to a wide range of odorants.
- Worker ants and female alates exhibit distinct odor detection patterns, indicating caste-specific olfactory tuning.
- The study identifies specific compounds to which each caste responds more strongly.

## Abstract

Ants, like many other social insects, rely on complex chemical signals to organize their colonies, coordinate tasks, and respond to threats. Their sense of smell plays a key role in detecting these chemical cues. In this study, we measured how the red imported fire ant’s antenna responds to 62 different odor cues using a highly sensitive recording method. We found that a type of sensory hair on the antenna can detect a broad range of odors. Importantly, worker ants and winged females showed different patterns of odor detection, suggesting that each caste has smell-based abilities suited to its role in the colony. These findings may help guide the development of new attractants or repellents for fire ant management.

The red imported fire ant, Solenopsis invicta Buren, is a eusocial insect that relies on a sophisticated chemical communication system for colony organization and function. Its olfactory system is vital for detecting semiochemicals in the environment. This study utilized single sensillum recording (SSR) to assess the olfactory neuronal responses of female alates and workers from basiconica sensilla exposed to a panel of 62 individual pheromones and general odorants, including terpenes, terpenoids, pyrazines, pyridines, ketones, aldehydes, alcohols, acids, aliphatic and aromatic acetates, benzoates, benzyl esters, and three essential oils. Basiconica sensilla, which contain multiple olfactory receptor neurons (ORNs), exhibited moderate to strong responses to most of the tested compounds, demonstrating a broad sensitivity to all odorants elevated. Comparative analysis of the two castes revealed that ORNs had similar responses to 47 odorants; however, workers showed stronger responses to nine specific compounds, while female alates responded more strongly to six others. These differences underscore the caste-specific olfactory tuning, likely reflecting their distinct roles within the colony. This study presents the first comprehensive mapping of basiconica sensilla responses to general odorants in S. invicta female alates and workers, enhancing our understanding of the S. invicta chemical ecology and potentially contribute to more effective fire ant management strategies.