The world is a mean, dangerous place when you're a slow-moving, soft-bodied beetle larva. Predators lurk just beyond the next leaf, parasitoid wasps want to use you as a living egg incubator and even the elements can drown or desiccate you. But for those who are resourceful, all that hardship breeds invention. In the leaf beetle family (Chrysomelidae), the larvae find (relative) safety under a protective shield of their own making ... constructed with material that’s as abundant and as easily, er, expelled as they get: their own poop. 

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Larva of the sumac flea beetle (Blepharida rhois) tucked in safely under its shield of poop. Image credit: Kurt Komoda, Flickr

'Faecal shields' (that’s the scientific term and we’re sticking with it because it’s awesome) are as diverse as the beetles that make 'em. In fact, the larvae of thousands of species are probably squirming about somewhere on the planet at this very moment, all brandishing some creative form of poop protection. And if the thought of studying them sounds like something you'd like to do, you'll be pleased to know this area of research seems to have its own name: fececology (hat tip to The Bug Geek for that one).

“In fact, the larvae of thousands of species are probably squirming about somewhere on the planet at this very moment, all brandishing some creative form of poop protection”

So why use poop? For a humble beetle larva, it’s a pretty ingenious self-defence strategy: you can get to work on pooping out your own protection just as soon as you hatch (some species have a completed shield in place in only 12 hours) and there’s never a shortage of material for future extensions or repairs. As they moult, some larvae will weave in bits of leftover exoskeleton to bind and strengthen their constructions.

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A larva of a tortoise beetle carries its poop like a protective umbrella. Image credit: Richard Comont, Flickr

And just how creative do those constructions get? Many are basic blobs or slimy piles, but others are carefully woven from single, dry strands to form a snug little thatch or an artfully twirled assemblage (and for one of the most amazing examples we've seen, check out this guy). Some shields are raised above the body (umbrella, anyone?) and can even be moved about and wielded at predators like a tiny, putrid battleaxe. And in the ultimate feacal flourish of ingenuity, the larvae take things a step further by combining their shield-making craft with chemical warfare. According to University of Colorado professor Jeff Mitton, they imbibe a special cocktail of defensive compounds from the plants they eat to give their poop added potency. Toxic to most insects, the compounds are expelled in the larvae's excrement, making for a building material that’s not only plentiful and convenient but also tainted with potentially deadly chemical agents. 

Despite all their benefits, faecal shields are not perfect: carrying them around can take its toll and beetle researchers sometimes disagree on just how effective they are against predators (some predators, for example, have evolved crafty strategies of their own to break through even the most solid shield). But let's give credit where it's due: leaf beetle larvae really do know how to make the most out of a pile of crap. Just look at 'em:

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