JULY
1993

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

7-22-93

Leaf look-alikes: Not a fashion statement

Insects have honed the art of disguise to within a gnat’s eyelash of perfection. A good disguise is one way some insects avoid becoming a meal for other animals. The “I look like a leaf” routine is one of the most common insect charades.

Insects called leaf-footed bugs get their name because they have legs shaped like leaves. This characteristic helps them blend into the vegetation where they are commonly found.

Another group of insects that looks like leaves are appropriately called leaf insects. These tropical insects are closely related to insects that mimic another plant part, walking sticks. Leaf insects have bodies, legs, and wings shaped like various-sized leaves. Some of the pseudo leaves making up the insect even appear to have a midrib and cross veins just like the real thing.

Katydids and tropical bush crickets also imitate leaves. The forewings of these insects are not used for flying, so they don’t have to remain aerodynamically correct — much the better for perfecting a disguise. Some of the wings of these insects have discolored spots as if the leaf had been damaged by disease. Some even appear to have begun to turn brown, as would a leaf before it falls from a plant.

Some of the leaf imitators enhance the illusion by swaying as if driven by a breeze. One such insect is the Australian stick insect. When disturbed, all the individuals in the area began to rock gently as if to say, “Nobody here except us leaves blowing in the wind!”

Some tropical mantids also exhibit elaborate leaf designs. Mantids are predators on other insects , but they don’t hunt; they wait for prey to come within their grasp. For mantids, good camouflage means dinner is more likely to walk or fly within grasp. However, mantids themselves can become meals for other animals, so their disguise also helps protect them.

Some butterflies also have evolved to look like leaves. However butterflies almost always mimic brown leaves. Apparently their scale coloration does not lend itself to green colors. 

The comma butterfly looks exactly like a brown, tattered, dead leaf. Someone discovering the comma butterfly for the first time will be surprised to see the dead leaf fly off when disturbed!

Another leaf mimic among the butterflies is called the dead-leaf butterfly. This butterfly is found in India and has bright orange, brown, and blue colored upper wings. However when the wings are folded, the undersides make the insect appear as a dead leaf, complete with veins and a diseased spot or two. These insects frequently rest among dead leaves, a behavior that enhances protection.


For insects that look like leaves, their attire is not just a back-to-nature fashion statement. Leaf mimicry to an insect is a life and death matter.

 

Writer: Tom Turpin
Editor: Andrea McCann