The Devil’s Bug of Choice -- by Peter Morton -- Muhlenberg College Class of 2014

Stick insects have a variety of nicknames, such as stickbugs and walkingsticks, but few are as incendiary as “The Devil’s Darning Needle, The Witches Steed, and The Devil’s Riding Horse”. While imagining the king of demon’s himself somehow manufacturing a saddle that would be conducive to the stick bug’s curious body frame is amusing, these animals are about as docile as they come. Their main defensive mechanic is to avoid predators by impersonating a stick, which I have found to be a relatively submissive being, on the whole. Maybe the fear they inspired is, in part, due to those would fell for this Beelzebug’s charade. Seeing a stick “coming to life” could create some terror, I’ll admit it. Despite all this bad press, however, the physically harmless stick bugs of the order Phasmatodea have managed to discover some amazing and devious methods of avoiding predators and having large numbers of offspring.

There are two distinct ways that animal camouflage themselves. The first, mimicry, involves the animal manipulating its  body to match its surroundings, effectively “blending in” and avoiding detection. Crypsis, the second type of camouflage, involves the organism acting like another part of its environment, to convince a predator that it is not a food item. Walkingsticks have somehow managed to master both types, making them truly an Olympic level wallflower.

The Stick Insect’s exoskeleton (Hard shell like skin!) will tend to be pigmented towards the environment they spend their time in, letting them naturally fade into the background. However, their ability to create mimicry extends beyond this feat. Some species of stick insects are actually capable of slowly altering the color of their skin possibly to better match a new environment versus an old day by day. They can also show off their ability as innate fashionistas, able to don lichen-like markings on their exoskeleton as another means of becoming one with their background.  In contrast with an Armani collection, these characters looked-over, rather than looked-at.

 Perhaps their more interesting camouflage, however, is their ability to actually mimic a stick in the wild, as a form of crypsis. Walkingsticks eat during the night. During the day, they become one with their inner stick by softly swaying if there is wind present in the same way a real stick would to fool predators. If the greatest feat the devil ever achieved was convincing the world that he didn’t exist, maybe there is some sharedlineage between the prince of darkness and the lesser known stick bugs.

But some of the true guile of a stick bugs lies in the way they protect their young. Interestingly enough, this requires no direct supervision from ma’ or pa’ stick insect. Most stick bugs are parthenogenic, meaning females do not require males to create more females. When a female stick bug performs this act, she will carefully place one egg on the forest and then move elsewhere to repeat the process. In this way, female stick bugs parade these eggs as seeds rather than developing larvae. In appearance, they are incredibly hard to tell apart from seeds from trees from the surrounding foliage, such as oak. And since they are placed very far apart from each other, predators often will not recognize the seed as an egg, because many insects lay their eggs in huge numbers in the same place. When they hatch, most species of stick bug are programmed to furiously run up the first vertical object, which are most often trees. They will then spend their time lounging and growing, till they master the art and science of being a twig. A few species of stick insects, however, have developed an even more ingenious way to protect their young. Each egg laid will have a fatty “capitulum” hanging off the side of the larva. Ants recognize this capitulum as a food source, and will carry it back to the hive to eat, surprisingly without disturbing the larva. Once the stick bug erupts from the egg, it somehow manages to just waltz out of the hive, refusing to overstay its uninvited welcome. In this way, they are protected from predators when they are at their most vulnerable.

Although they do not directly harm humans, some of their eating patterns have shown to be troublesome across America. When stick insects feed on trees, of which some prefer oaks, they will “skeletonize” the leaves of the tree. This process involves eating all parts of the leaves on the tree except for the veins, potentially killing it.  Stick Insects have been able to do serious damage to the Ozark Mountains of Arkansas and Missouri, but only in species that swarm. Residents of the Lehigh Valley should be aware that there certain ecological laws often disallow the owning of certain stick bugs, depending on whether or not they naturally occur in the area of purchase. This is because species foreign to an area can sometimes serve as pests, skeletonizing unfamiliar foliage without any already existing predation to keep them in their place. However, this doesn’t exactly limit the trade of stick bugs via the World Wide Web. Many websites illegally sell stick insects without any regard to where they’re sending it.  They might as well launch walkingsticks from a cannon in randomized directions. Lehigh Valley-goer, beware; do NOT purchase stick bugs without a permit. If they are released and are able to make a foothold in the area, we could be looking at landscape entirely inhabited by sticks with, oddly enough, no trees.

Prophecies of tree-mageddon aside, Stick Insects are an incredible look into the clever, deceptive, and whimsical methods mother nature can employ to protect some of its most subtle and docile creatures. I would recommend everyone throw aside the negative, and sometimes demonic, connotations of stick insects (and to a certain degree insects in general) and embrace them fully. Investigation into insect physiology and behavior can truly inspire wonder and marvel into a person that may have thought they were previously without.                  

The Devil’s Bug of Choice by Peter Morton is licensed under a Creative Commons Attribution 4.0 International License.