BBC Wildlife Magazine - - Beetles -

‘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.

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