One of the fantastic insects that camouflage as plants are Walking sticks, or stick insects. Stick insects are actually not a single species, but an entire order of insects that have evolved to resemble twigs and branches of plants to escape predators. They escape predation by blending into plant material. As their name suggests, they look just like sticks, and may even sway back and forth to more closely resemble a twig moving in the wind.
If you are thinking they might be small in size and can be ignored, you are in for a surprise. Depending on the species, walking sticks can grow from 1 to 12 inches (2.5 to 30 centimeters) long, with females usually growing bigger than the males. Did you know that stick insects are the biggest insects in the world—one species measures over 20 inches (51 centimeters) long with its legs outstretched.
They are quite common too. Walking sticks are found on every continent except Antarctica. They mostly live in temperate and tropical regions. Within these areas, the stick insect usually inhabits woodlands and tropical forests, where it hides on trees in plain sight. Walking sticks are a favorite food of many animals, but perhaps their most effective predators are bats. Most bats hunt by echolocation rather than sight, so they aren’t fooled by the insect’s stick-like appearance. As they are pushed to take their game to one step higher, when camouflage isn’t enough, some species have evolved the ability to release foul-smelling chemicals to deter predators, and others can secrete a liquid that temporarily blinds their foes. Others drop their legs when a predator attacks, but can regrow the appendages. Some species are winged and flash brightly colored patches under their wings to confuse predators.
Walking sticks are one of many species that can reproduce parthenogenetically, meaning the females can produce unfertilized eggs that hatch and grow into new females. Females lay eggs that look like seeds, and they have numerous egg-laying mechanisms to keep predators away. Some females lay eggs in places that are hidden or hard to get to. Others drop eggs one by one on the ground so they’re not all in one place for a predator to find. Newly hatched walking sticks reach adult size once they’ve undergone several molts. They reach maturity between three months and one year and usually live up to two years. So the next time you think you are seeing a stick, take a closer look as it might be walking away!
Photo by Museum Victoria