Variation in social and sexual behaviour in four species of aposematic seed bugs (Hemiptera: Lygaeidae): The role of toxic and non-toxic food

• We examine the effect of diet on the behaviour of four species of aposematic bug.
• We compare aggregation and mate choice in individuals fed toxic vs. non-toxic food.
• Contrary to predictions diet had little effect on social behaviours.
• Lygaeid behaviour may be consistent across different internal states.
• Automimicry may play an important role in these species.

Understanding variation in social behaviour both within and among species continues to be a challenge. Evolutionary or ecological theory typically predicts the optimal behaviour for an animal under a given set of circumstances, yet the real world presents much greater variation in behaviour than predicted. This variation is apparent in many social and sexual interactions, including mate choice, and has led to a renewed focus on individual variation in behaviour. Here we explore within and among species variation in social behaviour in four species of aposematic seed bug (Lygaeidae: Hemiptera). These species are Müllerian mimics, with characteristic warning colouration advertising their chemical toxicity. We examine the role of diet in generating variation in two key behaviours: social aggregation of nymphs and mate choice. We test how behaviour varies with exposure to either milkweed (a source of defensive compounds) or sunflower (that provides no defence). We show that although the four species vary in their food preferences, and diet influences their life-history (as highlighted by body size), social aggregation and mate choice is relatively unaffected by diet. We discuss our findings in terms of the evolution of aposematism, the importance of automimicry, and the role of diet in generating behavioural variation.