# Patrolling and Cleaning: Threat Detection and Response Behaviors of Soldiers in a Social Aphid

## TL;DR

This study explores how social aphids on secondary hosts detect and respond to threats, revealing new insights into their cleaning and defense behaviors.

## Contribution

The study reveals threat response behaviors in social aphids on secondary hosts, including patrolling and cooperative cleaning.

## Key findings

- Ceratovacuna lanigera soldiers patrol to detect threats like hardened honeydew and predator eggshells.
- Soldiers use frontal horns to remove threats and transport them away from the colony.
- The behaviors suggest ecological and evolutionary significance of altruistic actions in social aphids.

## Abstract

Threat response behaviors (housekeeping and colony defense) have been widely reported in social aphids inhabiting galls on primary hosts. However, little is known about whether social aphids that live exclusively on secondary hosts exhibit threat response behavior and the processes by which they perceive potential threats. This study provides a detailed description of the threat response behavior exhibited by the social aphid Ceratovacuna lanigera Zehntner, 1897 (Hemiptera: Aphididae: Hormaphidinae) on its secondary host. The more complete behavioral patterns include patrolling to detect potential threats (e.g., hardened honeydew, corpses, and predator eggshells), using frontal horns to remove threats, and cooperation among individuals. These findings offer deeper insights into the threat response behavior of social aphids and their ecological and evolutionary significance.

Housekeeping and colony defense behaviors are crucial for social aphids, as they help maintain a habitable living environment and enhance their ecological adaptability. However, over the past decades, numerous studies have focused on housekeeping and colony defense behaviors in species living in primary hosts, but little attention has been given to the secondary host stage. This constrains a deeper understanding of the altruistic behavior of social aphids, as well as the ecological and evolutionary significance of such behavior. We employed indoor video recordings to document and analyze the behaviors displayed by the soldiers of the sugarcane wooly aphid, C. lanigera, on secondary hosts. C. lanigera soldiers continuously patrol around the colony to detect potential threats. When encountering potential threats or obstacles, soldiers actively initiate cleaning behavior. The soldiers use their frontal horns to disengage the hardened honeydew, corpses, or honeydew simulants (rock sugar) that are attached to the surface of host plant leaves. Subsequently, they transport these materials away from the colony using their frontal horns or forelegs, either discarding or flicking them directly. When soldiers identify obstacles—such as predator eggshells—as natural enemies, they attack them with their frontal horns. Our findings contribute to a broader understanding of altruistic behavior in social aphids and the evolutionary success of their sociality.