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10 Cool Facts About Stick Insects

Interesting Behaviors and Traits of Stick Insects

By

Prairie walking stick.

Prairie walking stick.

Photo: © Whitney Cranshaw, Colorado State University, Bugwood.org

When I was little, I believed that stick insects were so poisonous you could die just by brushing your hand against one. I'm not sure where I got that idea, but it's not true, it turns out. These 10 facts about stick insects, on the other hand, are true.

1. Stick insects can shed and regenerate their limbs to escape attacks by predators.
Should a bird or other predator grab hold of a stick insect's leg, it can still make an easy escape. The stick insect simply gives up the leg, using a special muscle to break it off at a weak joint. Juvenile stick insects will regenerate the missing limb the next time they molt. In some cases, adult stick insects can even force themselves to molt again to regain a lost leg.

2. Stick insects can reproduce parthenogenetically, without the need for males.
Stick insects are a nation of Amazons, able to reproduce almost entirely without males. Unmated females produce eggs that become more females. When a male does manage to mate with a female, there's a 50/50 chance their offspring will be male. A captive female stick insect can produce hundreds of all-female offspring without ever mating. There are species of stick insects for which scientists have never found any males.

3. Stick insects not only look like sticks, they act like them, too.
Stick insects are so named for their effective camouflage among the woody plants where they feed. They're typically brown, black, or green, with stick-shaped bodies that help them blend in as they perch on twigs and branches. Some even wear lichen-like markings to make their disguise more authentic. Stick insects imitate twigs swaying in the wind by rocking back and forth as they move.

4. Stick insect eggs resemble seeds scattered about the forest floor.
Stick insect mothers aren't the most maternal of insects. They typically drop eggs randomly on the forest floor, leaving the youngsters to whatever fate befalls them. Don't be so quick to judge mama stick insect, though. By spreading her eggs out, she lessens the chance that a predator will find all her offspring and eat them. Her eggs resemble seeds, so carnivorous predators will be less likely to take a closer look. Some stick insects actually make an effort to hide their eggs, sticking them to leaves or bark, or placing them in the soil.

5. Nymphs usually eat their molted skin.
Once a nymph has molted, it's vulnerable to predators until its new cuticle darkens and hardens. The castoff skin nearby is a dead giveaway to enemies, so the nymph will quickly consume the shriveled exoskeleton to get rid of the evidence. The stick insect nymph also recycles the protein by eating its molted skin.

6. Stick insects don't bite, but they aren't defenseless.
If threatened, a stick insect will use whatever means necessary to thwart its attacker. Some will regurgitate a nasty substance that will put a bad taste in a hungry predator's mouth. Others reflex bleed, oozing a foul-smelling hemolymph from joints in their body. Some of the large, tropical stick insects may use their leg spines, which help them climb, to inflict some pain on an enemy. Stick insects may even direct a chemical spray, much like tear gas, at the offender.

7. Stick insect eggs may attract ants, which then collect and store the eggs in their nests.
Stick insect eggs that resemble hard seeds have a special, fatty capsule called a capitulum at one end. Ants enjoy the nutritional boost provided by the capitulum, and carry the stick insect eggs back to their nests for a meal. Once the ants feed on the fats and nutrients, they toss the eggs onto their garbage heap where they continue to incubate safe from predators. As the nymphs hatch, they make their way out of the ant nest.

8. Not all stick insects are boring brown.
Some stick insects can change color, like a chameleon, depending on the background where they're at rest. Stick insects may also wear bright colors on their wings, but keep these flamboyant features tucked away. When a bird or other predator approaches, the stick insect will flash the vibrant wings, then hide them again, leaving the predator confused and unable to relocate its target.

9. Stick insects can play dead.
When all else fails, play dead, right? A threatened stick insect will abruptly drop from wherever it's perched, fall to the ground, and stay very still. This behavior, called thanatosis, can successfully discourage predators. A bird or mouse may be unable to find the immobile insect on the ground, or prefer living prey and move on.

10. Stick insects hold the record for longest insects in the world.
In 2008, a newly discovered stick insect species from Borneo broke the record for longest insect (which had previously been held by another stick insect, Pharnacia serratipes). The Chan's megastick, Phobaeticus chain, measures an incredible 22 inches with legs extended, with a body length of 14 inches.

Sources:

  • Insects: Their Natural History and Diversity, by Stephen A. Marshall
  • The Insects: An Outline of Entomology, by P.J. Gullan and P.S. Cranston

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