Nature may look serene from a distance, but beneath the surface lies a brutal world of parasitism, venom and slow-motion predation. Some creatures don’t just kill their prey – they invade them, hijack them, liquefy them or devour them from the inside out while they’re still alive.
From wasps that turn spiders into living incubators to aquatic hunters that drink their victims like smoothies, here are five gruesome, deadly animals that consume their prey from within – proof that in the natural world, the most disturbing predators are often the smallest.
5 gruesome, deadly animals that kill and eat their prey from the inside
Tarantula hawk
Following mating, a female tarantula hawk will lie in wait outside the burrow of a tarantula or other large spider, tapping on the ground or strumming on a web to tempt her victim to emerge. After what might turn out to be a long fight – the tarantula hawk is often much smaller than its prey – she will use her long stinger to inject a powerful venom into the spider’s thorax.
This venom paralyses the spider but crucially does not kill it – the tarantula hawk needs it alive to feed her larva. She drags the spider to its own burrow or into one she has prepared (this may be some distance away), lays a single egg on the spider’s body, and leaves, covering up the entrance after her.
Three or four days later, the egg hatches and the tarantula hawk larva burrows into the still-alive spider’s abdomen. Over the course of about three weeks, the larva consumes the spider bit by bit, going through five growth stages. The spider only dies once the larva has eaten its vital organs, which it leaves until last. It then spins a cocoon and pupates for 15-20 days, ultimately emerging from the spider, and then the burrow, as an adult tarantula hawk.
Trinidad giant water bug
Most aquatic insects avoid fish. Yet Trinidad's giant water bug Lethocerus maximus hunts them, along with frogs, salamanders and other critters.
Often nestled among vegetation near, on or under water, it typically catches prey by surprise, latching on to a passer-by with hulkish raptorial legs, sinking a dagger-like beak into the victim and injecting a blend of tissue-eating enzymes that liquefy its insides. The bug then sucks up the puréed body parts like a protein shake. It attacks anything that moves – even humans, hence its nickname 'toe-biter'.
Caterpillar parasitic wasp
Life gets pretty grim for a caterpillar if it becomes infected with a parasitic wasp, says Nick Baker. The infection hijacks and chemically disables the caterpillar’s defences, altering its immune system and controlling its growth and behaviour to suit its parasitic crew. Over the next two weeks the larvae slowly consume their host from the inside-out, leaving only the essential organs, to keep the surrogate womb ticking over.
When they are fully grown, they paralyse the host and start to rasp at the inside of the caterpillar’s skin with tooth-like projections around their mouths, before bursting out in a grizzly mass extrusion. But that still isn’t the end of the caterpillar – the larvae have one task left for it.
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The virus corrupts the caterpillar’s behaviour, so rather than limping off to die, it spins a silken pad over the top of the fuzzy mass of Cotesia cocoons. Here it stays put. The zombie security guard protects its killers for another 10 days.
Sea spider
There are over 1,300 species of sea spider (Pycnogonida) found in every ocean on the planet – from the tropics to the poles (although they’re more abundant in polar regions), and from rockpools and shallow waters to the deep sea.
Perhaps the most horrifying thing about these animals is how they eat. Sea spiders use a tube called a proboscis to feed on soft-bodied animals, such as worms or sea anemones. They pierce the bodies of their prey with this proboscis “and they’ll suck up the guts and bodily fluids to ingest,” says OceanX, like slurping up a smoothie.
Sea lamprey
The first thing you notice about a sea lamprey is its remarkable mouth. It’s a perfectly round, sucker-like disc, wider than its body and lined with concentric rings of pointy little teeth.
It expertly uses this appendage to attach itself to other fish and marine mammals, piercing their flesh with its file-like tongue to feed on their fluids, a habit that has given rise to colourful monikers such as ‘vampire eel’ and ‘eelsucker’. This grisly behaviour is rarely documented as it occurs only among the sea-dwelling adults.
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