SEPTEMBER
2010

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

09-23-10

Download the audio of On Six Legs: MP3, WMV.

When Is A Walking Stick Not A Cane?


A riddle is a mystifying, sometimes misleading puzzle asked as a question and requiring ingenuity to answer. Riddles have probably existed for nearly as long as language itself. For sure, riddles existed in biblical times and were common in Old English poetry.

One biblical riddle is associated with Samson finding a swarm of honey bees in the carcass of a lion that he had killed with his bare hands. The event was the inspiration for Samson's riddle: "Out of the eater something to eat. Out of the strong something sweet." The answers? "What is sweeter than honey? What is stronger than a lion?"

Old English examples of riddles from the 10th century are included in the so-called Exeter Book. One example begins, "A moth ate words" and ends with "Not a whit the wiser was he for having fattened himself on those words." Unlike a lot of pun-type riddles the answer is not obvious. It is up to the listener to glean a conclusion.

Most of us remember trying to figure out riddles as we were growing up. And then when we heard the answer the response was something like, "duh!" Remember these? What is black and white and red all over? In case you forgot, that would be a newspaper. When is a door not a door? When it is ajar!

Let me pose a riddle for your consideration. When is a walking stick not a cane? Give up? When it is an insect, that's when!

Yes, the walking sticks that humans use are also known as canes, and some insects are called walking sticks. The name for these creatures isn't based on usefulness in helping humans walk, but because they resemble sticks, and they do walk.

Walking stick insect on branches
Walking stick, photo by
Robert Sisson

Today most scientists classify walking sticks of the insect kind in the order Phasmatodea. There are about 3,000 different kinds of insect walking sticks. Sometimes called stick insects, these creatures resemble twigs—and sometimes even the leaves—of the plants on which they feed.

Walking sticks vary in size. Some are only about a half-inch long. Others are some of the largest insects in the world and measure over 20 inches in length. Some insect walking sticks have wings while others are wingless. In some species the males have wings while the females do not.

The physical structure of walking stick insects is a natural camouflage system. These insects blend into their environments so completely that many times they go unnoticed by the casual observer. Even insect-eating birds fail to notice walking sticks. There is even a photo or two showing a small bird perched on an insect walking stick that the bird had mistaken for a twig.

Austrailian walking stick insect
Austrailian stick insect

In addition to obvious camouflage stick insects have other methods of protection. Many remain motionless as they cling onto plants during daylight hours. A few species have leaf-like legs; these species will actually sway when hanging from a leaf in order to resemble leaves swaying in the breeze. One species that does this is called the Australian stick insect. A cage full of Australian stick insects can sometimes be induced to exhibit the swaying behavior by a shout. Following the shout the insects start swaying as if to say, "Nobody here—just us leaves swaying in the breeze!"

Another method of protection is the presence of spines on some stick insects. Not only do the spines on their bodies and legs make them look fearsome, the stick insects use the protrusions to poke a predator that might have discovered them.

Walking sticks feed on leaves. Most species of walking sticks are found in the tropics. However temperate regions are home to a few species of walking sticks. Generally, though, most people don't see the insects because of their camouflage and the fact that many feed high up in trees. In Indiana, spectacular populations of walking sticks are sometimes found in oak forests. These insects can be so thick in the trees that a person standing below them is bombarded with eggs and insect manure, called frass, falling like rain into the leaf liter.

So if the idea of being awash with falling insect frass is not your idea of a good time, it would be best to avoid standing in a grove of oak trees infested with a batch of walking sticks of the insect kind.

 

Writer: Tom Turpin
Editor: Olivia Maddox