BEETLES ARE MASTER ALCHEMISTS
‘Do not eat beetles’ is a widely held mantra throughout the animal kingdom, and for good reason. Take the bombardier, Brachinus crepitans. It is named for the audible cannon-report ‘pop’ it makes when it squirts boiling-hot benzoquinones into the face of its wouldbe attacker. These are mixed in a reaction chamber in its abdomen, then fired through a directional anal sphincter. Ants are this beetle’s main adversaries and a toad will vomit it up when its stomach starts to burn.
Poisonous distastefulness is usually advertised by bright warning colours. But ladybirds, which are unpalatable to most birds, also teach potential predators a lesson to save being chomped. They squeeze their noxious orange or yellow blood through special pores in their knees, a defensive strategy called reflex bleeding. Some Mediterranean ( Mylabris) and North American ( Epicauta) oil beetles are so toxic if they are caught in silage or hay and accidentally eaten by a cow, the mammal not only dies a painful death, its meat is too toxic for human consumption. The toxin, cantharidin, was once extracted to take as an aphrodisiac. It causes supposedly erotic tingling. But more often it results in death. At night, warning colours are apt to be overlooked, which is why glow-worms and fireflies evolved light signalling. Today, their cold chemical glows and flashes send messages between males and females.
Above: Photinus carolinus fireflies light up the night sky above a tent in Tennessee, USA. Left: a bombardier beetle protects itself by squirting a noxious chemical spray.