This video from the USA says about itself:
American Oil Beetles – Blister Beetles
14 October 2017
Do not ever touch these beetles! Bizarre bugs indeed! I happened upon about a dozen of these beauties in a fall mating frenzy centered around two very large females full of eggs.
Fortunately I did not step on them in the middle of the trail. They are called Blister Beetles because they emit an oil that will burn the skin if you pick them up. The poison they contain is among the strongest known. Cantharidin is an odorless, colorless fatty substance of the terpenoid class, which is secreted by many species of blister beetles. It is a burn agent or a poison in large doses, but preparations containing it were historically used as aphrodisiacs. In its natural form, cantharidin is secreted by the male blister beetle and given to the female as a copulatory gift during mating. Afterwards, the female beetle covers her eggs with it as a defense against predators.
Research has illuminated the piecemeal patterns of recolonization among a hardy species of beetle regularly affected by managed burns: here.