Hey! That’s Not a Stick

I recently saw what I thought was a clump of dried grass stuck to my window. I couldn’t maneuver to see it more closely, so I used my phone to take a photo. I’m glad I hadn’t just reached down and yanked it out. Because… delightedly, I realized that this tuft might be a walking stick insect!

How Can a Stick Walk?

Researching walking sticks in the Sonoran Desert, I concluded that this is a Diapheromera arizonensis, the Arizona walking stick. Walking sticks are known for their unique use of camouflage to avoid predators, such as birds, reptiles, and spiders. But not all predators fall for those same tricks. 

One such predator is bats (by the way, I’m working on a book or two about them). The walking sticks’ camouflage doesn’t help them against these nocturnal predators. Bat echolocation easily identifies the insects’ noise, resulting in consumption. Walking sticks are very nutritious as food.

So, if camouflage doesn’t work, how else do these tasty insects protect themselves? If pecked by a bird, the walking stick will become motionless and fall as if it’s merely a stick. If that isn’t enough, they release distasteful chemicals from various body parts.

I thought this walking stick may have been the victim of a spider, perhaps having been caught in its web down in the corner. 

Thinking about the long, stick-like body, I wondered if they also might be ambush hunters, but they’re herbivores. There’s no need to sneak up on plants. Walking sticks tend to be active at night, hiding out during the day, like this one. I suspect this is a female since only one 1 in 1,000 is male. This isn’t a problem for the species, since the females can lay fertile eggs that produce female offspring. This is called parthenogenesis. Parthenogenesis is seen as well in my favorite group of animals, reptiles.

Another similarity to reptiles is the ability for autotomy. Autonomy is a defensive adaptation that gives them the capability to self-detach a body part when it is gripped by a predator. Better to lose a tail, in the case of lizards, or a leg in the case of a walking stick, than to be eaten! And amazingly, the body part is regenerated. Even though my walking stick could have regrown a leg, I’m glad I didn’t pull on one to determine if it was a tuft of grass or the amazing insect it was.

Another similarity to reptiles is that walking sticks have suction cups on their feet, like some lizards. They can walk up vertical surfaces as well as upside down!

The More We Know

Unfortunately, walking sticks have not been well studied, so their taxonomy is evolving. They were initially lumped together with other plant-looking insects, praying mantises, and cockroaches. Now, they have been divided into four families of their own. Further relationships will become more developed as these remarkable insects are studied more. About three thousand species of walking sticks have been identified so far, with expectations that more will be discovered. After all, it is hard to find insects that look like part of a plant.

Even though my Sonoran walking stick was only a couple of inches in length, other species can get quite long. The giant walking stick, Megaphasma denticrus, is believed to be the longest one in the United States, reaching up to seven inches. However, the biggest walking stick, Phobaeticus kirbyi, is found in Borneo and is the longest of all modern insects at thirteen inches!

 My walking stick was gone a couple of days later. I hoped it had moved on to a nice tree where it could enjoy the remaining portion of its two-year lifespan. 

If you are interested in learning more about the wonderful camouflage and defensive adaptations of other animals, take a look at my education workbooks!