Cantharidin world on bird droppings: Reused cantharidin after bird predation of cantharidin-producing insects

Cantharidin is produced only by beetles of Meloidae and Oedemeridae and represents a rare resource for canthariphilous insects that ingest fluids and/or portions of living and even dead meloid and oedemerid beetles. Although the physiological mechanism is unknown, these canthariphilous insects must have developed a superior ability to search for this rare resource in their habitats. They would be able to access cantharidin even in minute amounts. In this study, we found that canthariphilous insects are attracted to traces of cantharidin that remain in bird droppings after the birds have consumed meloid or oedemerid beetles. We succeeded in reproducing this phenomenon in the field by experimentally using quail droppings after giving meloid or oedemerid beetles. Thus, cantharidin was cycled from bird droppings to canthariphilous insects after being dispersed by birds widely and vertically in the cantharidin world consisting of cantharidin-producing insects and other interacting members via cantharidin.