Insects' essential role in understanding and broadening animal medication

Medication – the use of environmental substances to treat infectious diseases – has long interested humans. Observing such behaviors in non-human animals has increased our appreciation of cognition and plasticity across host species. Diverse relationships of insects with plants and parasites offer abundant opportunities to investigate such behaviors, while their spectrum of reproductive strategies and living arrangements – ranging from solitary to eusocial communities – allow understanding how medication behaviors affect inclusive fitness via effects on close relatives. Studying insects also advance knowledge of the context-dependent costs of expressing medication behaviors and the relationships between medicinal substances and the host’s innate immune system and microbiome. We highlight outstanding questions in these areas, focusing on costs and benefits in the context of inclusive host fitness.