# Mosquito Egg Raft Distribution Is Affected by Semiochemicals: Indication of Interspecific Competition

## TL;DR

Mosquitoes avoid laying eggs in water with signals from crowded competitors, showing they can detect and respond to interspecific competition.

## Contribution

This study shows mosquitoes use semiochemicals to detect and avoid interspecific competition during oviposition.

## Key findings

- Mosquito females avoid laying eggs in pools with crowding signals from other species.
- Low-density competitor larvae do not deter oviposition but attract conspecifics.
- The study reveals species-specific signal detection in mosquito habitat selection.

## Abstract

Interspecific competition occurs when two or more species require similar resources. Competition could be avoided by selecting a habitat with fewer competitors. While this behavior is well known, the identification mechanism is poorly understood. Mosquitoes select larval habitats during oviposition, and high competitor densities reduce larval survival. In this study, we show that ovipositing mosquito females can detect and avoid pools containing crowding signals originating from interspecific larvae. Furthermore, when larvae were not crowded, the habitat was found to be attractive to conspecifics. These findings increase our understanding of signals affecting mosquito oviposition, competitor recognition, and habitat selection under competition conditions.

Numerous species of animals alter their behavior in response to increasing competition. To do so, they must possess the ability to detect the presence and density of interspecific competitors. We studied the role of semiochemicals released by increasing densities of larval Culiseta longiareolata Macquart on female oviposition habitat selection in two field experiments. Similarly to C. longiareolata larvae, subordinate Culex laticinctus Edwards are periphyton grazers who dwell in rain-filled pools in the Mediterranean region. We show that C. laticinctus females oviposited significantly less in mesocosm pools that were treated with crowding signals originating from C. longiareolata larvae. In the second experiment, we placed a similar number of larvae directly inside the 50 L mesocosms. These low-density mesocosms did not affect C. laticinctus oviposition but were attractive to conspecific oviposition. These results increase our understanding of the female ability to detect species-specific signals, indicating increased larval competition.