Fall seems to be the time of year when I notice the walking stick.  This long, super slender, light brown insect looks very much like a twig–with legs.  Lately I have been seeing these critters here and there, always completely still, attached to one of the sliding screen doors to our house, to a tool shed wall, or to a deck post.  Often, I will notice the same walking stick still clinging, unmoving, to the same spot hours later.  

     I have been curious about these insects, so I decided to do a little research.  I learned that more than 2,500 species of walking stick are known to exist, and they are found throughout the temperate, and especially subtropical and tropical parts of the world.  Walking sticks live all over the U.S., although they are more abundant in the southern half of the country than in the northern half.

     As you might expect from the walking stick’s strong resemblance to a twig, both in shape and color, camouflage is the name of the game when it comes to survival strategies.   

     I am pretty sure that the reason I notice these insects on our house and shed but not on the trees is simply that the ones attaching themselves to trees are so well camouflaged that I fail to detect them.  But when a walking stick really wants to hide, it can draw in its legs, so that they are parallel to and flush with its body.  The walking stick then stiffen its body and drops to the ground.  There it may remain motionless, a dead twig, unnoticed by predators. 

     Not only is the walking stick able to ‘impersonate’ a dead twig on the ground;  it can even imitate a twig moving slightly in the breeze!  The insect achieves this feat by flexing its legs, which causes its body to sway slightly from side to side,  just as a twig might do in a breeze.

     Camouflage is also a key ingredient in the walking stick’s reproductive process.  For example, the eggs of many walking stick species look very much like the seeds of the particular species’ main host plant! 

     The female lays her eggs in the fall, one at a time.  She lays from one to several over the course of a day.  An egg may stick to a leaf of a tree or bush where she has attached herself, or an egg may simply fall to the ground.  Eggs are likely to hatch the following spring, but eggs may wait as long as years. if necessary, until conditions are right.  A walking stick typically lives for about a year. 

     Even if the female lacks a male partner, she can produce fertile eggs.   And these eggs are always female.  In fact, only one in 1,000 walking sticks is a male, scientists say.  

     Walking sticks are herbivores.   In the spring the newly hatched nymphs feed mainly on understory shrubs.  As the nymphs mature,  they eat throughout the crown of their host plants.  Among the many common trees favored as host plants by walking sticks in the U.S. are apple, basswood, birch, dogwood, hackberry, hickory, locust, oak, pecan, and wild cherry.

     Walking sticks often feed during the nighttime hours in order to evade detection by their predators, who include many birds, reptiles, primates, and bats.  But the walking stick’s nocturnal strategy and its camouflage do not work with bats.  Thanks to their echolocation or ‘radar,’ bats can relatively easily detect the whereabouts of a walking stick. 

     For the rest of this season, I think I will be looking more closely at the trees around me to see if I can see a walking stick ‘hiding out’ there.–April Moore

the American Walking Stick

 

 

 

This entry was posted on Tuesday, October 20th, 2009 at 6:02 pm and is filed under Insights and Visions on the State of the Earth. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.