The modulation of nutritional intake by animals to combat pathogens is a behaviour which is getting increasing attention. Ant studies using isolated compounds or nutrients in artificial diets have revealed a lot of the dynamics of the behaviour, but natural sources of medicine are yet to be confirmed. Here we explored whether Formica fusca ants exposed to a fungal pathogen can use an artificial diet containing foods spiked with different concentrations of crushed aphids for a medicinal benefit. We show that pathogen exposed colonies adjusted their diet to include more aphid supplemented foods during the acute phase of the infection, reducing the mortality caused by the disease. However, the benefit was only attained when having access to a varied diet, suggesting that while aphids contain nutrients or compounds beneficial against infection, it is a part of a complex nutritional system where costs and benefits of compounds and nutrients need to be moderated.

Ant nests (Formica fusca) were collected and given unique ID's

For experiments original nests were split into experimental colony fragments (80 workers/fragment) to be used in the different infection treatments (Sham treated Control or exposed to a fungal pathogen (Beauveria bassiana)). Each experimental colony were then given a diet consisting of three different concentrations of supplemented aphids (Megaoura viciae): High concentration, low concentration, standard food (no aphids)). Foraging arenas were photographed 5 times a day for 9 days, from which each foraging ant was counted on the specific foods. Dead and alive ants were counted at the end of the 9 day period.

For the second part, we split original nests into 4 experimental colony fragments to be used in different treatment diet combinations (Control - Standard food, Control - High concentration food, Exposed - Standard food, Exposed High concentration food). Dead ants were counted daily for 9 days.

All data processing and analysis was done using R.