Question: what's the best line of defense when you're old and crotchety and your body's not working quite like it used to? The answer, of course, is to turn yourself blue and explode when provoked. At least if you're a termite.
Worker termites' mouths will wear down from years (but really more like a year or two, tops) of hard labour. As they age, they start to build up blue rings on their backs, the blue colour because of a copper-binding protein. The stuff builds up under the cuticle over their lifetime, growing more and more poisonous as they age. And when they're in the twilight of their lives, what do they do if a rival termite approaches, ready to tussle? Rather than throw 'bows, er, mandibles that just don't work like they used to, the termite blows up, coating its enemy in a toxic goop. Imagine if your grandpa did that next time you told him it's no longer safe for him to get behind the wheels of his Vauxhall.
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