Camouflage at its best
A friend recently showed me a photo she took of a walking stick near her home. No, it’s not a cane to help one navigate rough terrain – it’s an insect. These delicate-looking creatures are not easy to find because their bodies act as camouflage against tree branches and twigs.
We had an abundance of them on our property about 20 years ago, but I can’t remember the last time I saw one. Their normal range is the hardwood forests across much of the northern part of North America. They are referred to as phasmid insects in the Phylliidae family, and other names are stick bugs or stick insects.
The family name comes from the Greek for “phantom” or “apparition,” referring to their resemblance to vegetation. They are wingless and use their body shape and appearance to blend in with the trees they forage on. They feed on living or dead plant material, but mainly the leaves of oak, cherry, hazelnut and sometimes black locust trees, eating the leaf tissue among the veins. That means they are skeletonizer insects. The main feeding time is between 9 pm and 3 am.
The long, thin body of the walking stick looks like a twig. The creature creeps slowly along a branch or over dead leaves and is not readily noticed. Its movements stop and start in a deliberately halting manner, and it becomes motionless when danger lurks. If that defense fails, the walking stick can eject a foul-smelling liquid that usually discourages predators.
Adult females tend to be larger – up to three and three-quarters inches – and they may have some green mixed in with the brown color. Males are all brown and smaller, reaching a length of three inches. Walking sticks have six legs, but the front two legs are often extended forward on the branch, helping them look even more like twigs. If a leg is lost, they can regenerate it. Few other insects and none of the higher animals can do this.
The female drops eggs – sometimes up to 100 – at random as she walks along. A quick-drying, waterproof, varnish-like fluid coats each egg when it’s laid, providing it with a highly protective case. The oval egg is about three millimeters long and is a polished black color with a whitish stripe on the side.
The eggs must be extremely durable because this is the only way walking sticks at this latitude can survive the winter. Hibernation takes place during the egg stage, when the eggs simply lie where they have fallen. The warmth of early spring brings about the hatching, when the young, which have been “folded” within the egg, emerge as nymphs that are about four and a half millimeters long, with a uniform, pale yellowish-green color: a perfect match for the new, green spring vegetation, which provides good protection from predators.
Like grasshoppers and field crickets, walking sticks go through an incomplete metamorphosis, with the nymphs hatching from the eggs and looking like miniature adults. They eat, grow and shed their skin only twice before reaching adult size. Hatching to maturity takes about six weeks. Young walking sticks are green and turn brown once they become adults.
In my research, I’ve found varying opinions about the colors: green for the young only or for females, and brown mostly for males. One reference says that if you see a green walking stick in late summer, it’s probably a male. The female will be brown to gray-brown to help her blend in with the trees.
There are more than 3,000 species of walking sticks in the world – many in the tropics – and some can grow to be 12 inches long. There are four other species that inhabit the southern parts of the United States.
Predators that eat these insects are birds, bats, spiders, reptiles and small mammals. Some creatures eat only the droppings of walking sticks.
Studies have found that, when kept in captivity, these creatures lived for about three years, with the females laying about 300 eggs during their lifetime. The female walking stick is one of the insects that can reproduce without mating, which is called parthenogenesis or asexual reproduction. It’s also common in a number of ants, bees and wasps. When a female walking stick mates with a male, only 50 percent of the eggs will be males.
If you happen to find a walking stick, take the time to appreciate its marvelous adaptation to its surroundings. The fascinating life histories of these native insects can add considerable pleasure to our existence on this planet and remind us that we humans are only one infinitesimal strand in the great web of nature.