Transmission of pathogens is facilitated in societies whose members are related and closely interact with each other. Rapid detection of, and response to, incoming pathogens is thus crucial to prevent infectious disease outbreaks. My previous work has shown that ant societies indeed react immediately to incoming pathogens by performance of collective disease defences, including antiseptic behaviours such as grooming of pathogen-exposed colony members and removal of diseased brood. This suggests that ants detect pathogens even before but also after infection, which has enormous evolutionary advantages at the colony level. My work on ants revealed that tactile pathogen cues are insufficient to trigger these responses, making chemical cues likely candidates. Moreover, pathogens seem to emit volatiles detectable by termites and honeybees, and ants possess a similarly sensitive olfactory system used in e.g. nestmate recognition and even have over-proportionally many olfactory receptor genes. I here aim to identify and characterize the nature and origin of cues that elicit collective antiseptic behaviours in ants, by combining behavioural observations, detailed chemical analyses and electrophysiological measures. I will further test how cue expression and perception depends on differences in caste, developmental stage and infection state, as well as genetic diversity. Using recent knowledge on the insect olfactory receptor system I seek to 1) understand the neurological processing of disease cues in ants and 2) develop a manipulative toolkit (e.g. RNAi) to suppress pathogen detection and thus performance of collective disease defences. This approach will enable direct assessment of the importance of a well-functioning olfactory sensory system in controlling disease outbreak at the colony level. The proposed project allows me to expand my research profile by using cutting-edge techniques in new disciplines to answer mechanistic questions of the evolution of social immunity