Preventing Transmission of Lethal Disease: Removal Behaviour of Lasius fuliginosus (Hymenoptera: Formicidae) Towards Fungus Contaminated Aphids

SIMPLE SUMMARY: To decrease the risk of infection transmission, ants are known to use a number of defensive mechanisms. One of them is the removal of conidia-contaminated aphids and sporulating cadavers, which is aimed at limiting contacts with potentially dangerous entities. This quarantining behaviour is helpful in limiting transmission of disease by the aphid milkers, both to the ant colony and among aphids, which are their main suppliers of carbohydrate food. The spread of this behaviour among ants is still scarcely studied. Among seven ant species studied, active usage of quarantining behaviour was found only in Formica ants. The behaviour of Lasius fuliginosus aphid milkers towards Chaitophorus populeti aphids covered with conidia of Beauveria bassiana was studied in the field. Most aggressive milkers quickly detected and removed conidia-contaminated aphids from the plant, carrying them down and placing them some distance away from the experimental aspen trees. In general, active usage of quarantining behaviour towards fungus contaminated aphids was found to be not limited to the genus Formica, but typical of L. fuliginosus as well. Removal of most fungus-contaminated aphids from the plant enables these ants to reduce the risk of infection transmission among aphids, as well as among ants. ABSTRACT: The ability of ants to detect and remove conidia-contaminated aphids, aimed at limiting contacts with potentially dangerous entities, is an effective antifungal mechanism to prevent the spread of infection among both their nestmates and aphids, their main suppliers of carbohydrates. However, the spread and the scale of this quarantining behaviour among ants are still scarcely studied. Among seven ant species studied, active usage of quarantining behaviour was found only in Formica ants. The behaviour of Lasius fuliginosus (Latreille) aphid milkers towards Chaitophorus populeti (Panzer) aphids covered with conidia of Beauveria bassiana (Balsamo-Crivelli) Vuillemin was studied in the field. Most aggressive milkers quickly detected and removed conidia-contaminated aphids from the plant, carrying them down and placing them some distance away from the experimental aspen trees. In general, active usage of quarantining behaviour towards conidia-contaminated aphids was found to be not limited to the genus Formica, but typical of L. fuliginosus as well. The response of milkers of L. fuliginosus and Formica s. str. ants to living aphids covered with conidia is quite similar. Removal of most fungus-contaminated aphids from the plant enables these ants to reduce the risk of infection transmission among both their nestmates and aphids.