Beetles in the genus Meloe are collectively known as oil beetles. The beetles sequester toxic cantharidins from plants that protect the beetles from predators. When disturbed, the beetles will “reflex bleed” or release droplets from the leg joints. The droplets (known as “oil”) contain the toxin. Predators can determine by tasting the droplet that the beetle is toxic. This spares the beetles from more harmful attack by the predator.Recently, The Mediterranean Oil Beetle, Meloe mediterraneus, last collected from the United Kingdom in 1906, was rediscovered near South Devon. The larvae of this beetle are triunglins that hitch rides on female bees for transport to the bee nest where they parasitize the bee larvae and consume their food. The recent find may be a new introduction from a bee blown across the English channel, or it could be that the beetle was simply overlooked.
Naturalist, John Walters, who has written a number of wildlife guides, has a keen interest in oil beetles and has a number of great photos on his website.