The Bombadier beetle, Brachinus crepitans, which may be seen flying from May to June in coastal areas of Southern Britain, has an amazing response to would-be predators. When disturbed or feeling threatened, it explosively sprays a strong liquid (consisting of a mix of hydrogen peroxide and hydroquinone at an estimated temperature of 100˚C) from the tip of its body with a loud ‘pop’.
One recipient of the beetle’s displeasure was Charles Darwin. He describes in his autobiography how, when collecting beetles at Cambridge in the late 1820s, I saw two rare beetles, and seized one in each hand; then I saw a third and new kind (a Crucifix ground beetle, Panagaeus cruxmajor, which was sheltering under a piece of bark on the banks of the River Cam), which I could not bear to lose, so that I popped the one which I held in my right hand into my mouth. Alas! It injected some intensely acrid fluid, which burnt my tongue so that I was forced to spit the beetle out, which was lost, as was the third one.
This incident left a long-lasting impression on Darwin. In his letter of 1846 to a fellow naturalist, the Reverend Leonard Jenyns, he describes how, when holding the Bombadier beetle between his teeth, to my unspeakable disgust and pain the little inconsiderate beast squirted his acid down my throat and I lost both Carabi and Panagæus!
Listed as an Endangered Species, the Crucifix beetle is nocturnal, sheltering during the day under pieces of wood and the like in the rich vegetation along the margins of standing or slow flowing water. It is found in very few locations in the UK.
