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African assassin bug

09/03/02 12:00AM By Ruth Page
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(Host) Can you imagine an insect that has double camouflage, one type to protect it from predators, the other to keep its own prey from noticing it? Ruth Page describes the creature.

(Page) There are sea creatures that have long seemed to me to be superior in camouflage even to most of our land-bound creatures, such as the zebra with her sun-and-shadow markings, or the stick insect who is so clearly a twig until he moves.

Now, though, I've read in Natural History magazine about the champion camouflager: the nymph of the African assassin bug Paradocla. Perhaps because the insect has evolved for countless centuries, it's had time to develop double-camouflage. The bugs don't want to be seen by their prey, but they also don't want predators to see them. And the same camouflage suit won't work for both.

So Paradocla learned to provide two camouflage suits to wear simultaneously. A nymph covers itself completely with dust by wriggling in the dry soil. That keeps the prey, ants, from seeing or smelling it; ants don't even notice the bug if they happen to touch it, because all the ant feels is dust.

Spiders and geckos both like a meal of assassin bug nymph. The nymph therefore lugs what the magazine calls a "backpack," a conglomeration of plant and insect remains. It shoves the scraps up onto its back and ties them there by secreting threads as wrappings.

Of course scientists couldn't reach any conclusion about all this without doing tests. They found predators attacked when assassin bugs' back-packs, but not the dust, were removed.

Then they examined the prey reaction when they dusted off the bugs but left the backpacks in place. The ant-prey quickly recognized the bugs as the enemy and scooted away.

This is the kind of thing that makes "thinking" such a puzzle. Insects are supposed to behave only by instinct. Yet to develop two different camouflage protections, each specific to its job, seems somehow intelligent.

No doubt these insects evolved over so many years, happenstance can get the credit. If some bugs were dusty by chance, and were survivors because they could prey on ants while their undusty companions went hungry, they would live to maturity. And it must be possible that some of the nymphs, crawling about in the soil duff, accumulated scraps of leaf and dead insects on their backs and were also survivors.

How in the world they developed a way to secrete threads to tie their backpacks in place is beyond my comprehension, but then so are many of Nature's accomplishments. It's hard not to believe that they had to "figure it out."

This is Ruth Page, flabbergasted as always at what Nature can accomplish without what we call intelligence.
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