Insect carrion and trapped live insects are attached to the surfaces of many plant species that have sticky or hooked trichomes or are sticky following the exudation of latex or resin when wounded. Direct physical/chemical defences by trichomes, resins and latex are well known. In addition, such attached carrion is known to attract predators that indirectly defend the plants against further insect attacks. I propose that, in addition, the attached dead or trapped living insects may serve as billboards: (i) cueing visually to other herbivores that the plants are already occupied; and (ii) cueing and signalling them both visually and by rotting carrion or stress volatiles emitted from trapped insects that such plants are dangerous and even deadly. This is a type of an extended phenotype (via insect bodies and volatiles), ‘second-hand’ plant aposematism, based on non-self but still plant-associated signals.

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