Ant-snatching assassin bug nymph (Acanthaspis sp.)

A pair of ant snatching assassin nymph found on the same branch. They were carrying ant corpses on its back after they fed on them. This is my second spotting of 2 nymph together. First sighting was in May 2016 melvynyeo.deviantart.com/art/A…

Quote from blogs.discovermagazine.com/not…
Robert Jackson and Simon Pollard from the University of Canterbury have been studying a pretender with a much more gruesome disguise – the ant-snatching assassin bug Acanthaspis petax, which covers itself with the corpses of its own prey.

The word ‘bug’ has a specific technical meaning – it refers to a group of insects, the Hemipterans, that have sucking mouthparts. Most, like aphids, use these to gulp plant sap but the assassin bugs use them for murder. They grab passing insects, stab them with their syringe-like mouthparts, inject paralytic saliva and digestive enzymes and suck up the broken-down bodily fluids.

Most species discard the lifeless husks but the ant-snatcher secretes fine sticky threads from its back and there it sticks the remains of its prey. An earlier study suggested that the assassin bug’s cadaverous backpack protected it from other predators and now, Jackson and Pollard have tested this theory by pitting the bugs against jumping spiders.

Jumping spiders are superb stalkers that use keen vision and accurate leaps to ambush prey. Jackson and Pollard let three species of jumping spiders loose upon either naked assassin bugs or those bearing ant-coats.

They found that the spiders attacked the naked bugs about ten times more than the covered ones, even if the bugs in question were actually dead and preserved.

The fact that the dead shielded bugs were just as uninviting as their living peers suggests that the disguise has nothing to do with a change in the bugs’ behaviour or motion but everything to do with the ants they carried. Clearly, when faced with a jumping spider, wearing a coat of dead ants can mean the difference between life or death to an assassin bug.

Why does it work? Unlike the decorator crabs, the assassin bugs weren’t plastering themselves with local wildlife to blend in. Certainly, the experiments were done in glass cages with no other ants around. Instead, Jackson and Pollard suggests that the ants break up the bug’s form so that instead of a characteristic shape that the spider can tag as ‘prey’, it sees a jumbled mess that doesn’t look like anything it has ever eaten before. It sees the bug, but doesn’t register it as a meal.

There is a final possibility though. Ants are not easy prey – they have chemical weapons and strength in numbers and many small predators give them a wide berth. So the bugs’ grisly defence may rely on using ants in particular and Jackson and Pollard are now putting this idea to the test.