Callum F. McLellan

Abstract Collective behaviour forms the basis for many anti-predator strategies. Within Lepidoptera, larval gregariousness has evolved convergently across many phylogenetically disparate lineages. While the selection pressures shaping variation in larval social behaviours are well investigated, much less is known about the mechanisms that control social attraction and behavioural coordination.

1 INTRODUCTION Many prey animals have evolved grouping behaviour in response to predation and resource availability. Lepidopteran larvae benefit from aggregating in a number of ways, ranging from increased protection from predators (Greeney et al., 2012; Hunter, 2000; Reader & Hochuli, 2003) to facilitated feeding (Campbell & Stastny, 2015; Clark & Faeth, 1997; Fordyce, 2003; Kawasaki et al., 2009; Rentería et al., 2022).

Abstract Larval Lepidoptera gain survival advantages by aggregating, especially when combined with aposematic warning signals, yet reductions in predation risk may not be experienced equally across all group members. Hamilton's selfish herd theory predicts that larvae which surround themselves with their group mates should be at lower risk of predation, and those on the periphery of aggregations experience the greatest risk, yet this has rarely been tested.