Animal Mundi: A Very Big Bug by TheFrogBag

A Very BIG Bug

written by Corinna of TheFrogBag

What do you consider a big insect? Half an inch long? An inch? House centipedes can get even bigger, a fact that makes them unwelcome guests in many people’s homes. But there are also folks like the woman who taught my first entomology class. She claimed that house centipedes “are just like little pets that you didn’t have to feed or walk.” She would have loved living in Australia, where at least one insect grows to over eight inches in length.

The goliath stick insect (Eurycnema goliath) is a member of the Phasmatidae family, and despite its large size it’s harmless. It is equipped with neither a venomous bite nor a stinger, although it does have large hooks on its back legs that could maybe leave a scratch. A more likely scenario is that it would simply leave the entire leg behind and escape without it, a fact that definitely makes the goliath the loser in that contest. 

Although relatively common around the city of Brisbane, even most Australians will never see a goliath. That’s because, despite their robust body size, they are masters of camouflage. Completely herbivorous, they spend almost all of their time hanging motionless on shrubs and trees. Their size is actually a benefit in this case since they tend to look just like a twig. The common name of “walking stick” suits them to a T. 

Other adaptations to this sedate lifestyle involve a unique swaying motion while moving (like a twig in the breeze) and the ability to fling their droppings far from the plant they’re resting on. Such a large animal processes a lot of leaves, so it would be easy for a predator to simply look for the mess on the ground and then look up. Goliaths foil this by using a long filament attached to their abdomen to hold the dropping as it is produced, and then, with a quick jerk, send it flying more than a meter away. Oddly, they allow their eggs to drop straight down, but this may well be an adaptation too. The eggs look a lot like seeds and are often picked up by ants, which may allow the young to hatch out safely underground, away from prying eyes. 

But what if, after all that patient hiding, a predator still spots a goliath? An insect of that size, neither toxic nor well-armored, is a real prize for a hungry bird. Well, it turns out that these walking sticks have one more trick up their sleeves. When surprised they open their wings, suddenly displaying a bright red color and a pair of eyespots on their thorax. The display usually makes the bird pause long enough for the goliath to parachute lower in the canopy or jump away.  

Sadly, here in the United States where I live, we don’t have anything even close in size to the goliath walking stick. We do have house centipedes though, in case you were starting to feel lonely.