• Gray’s twig, one of the world’s many stick and leaf insects, lives in eucalyptus and other trees across southern Australia. This species, Ctenomorphodes chronus, grows to a length of about 18 centimeters (7 inches). Like other stick and leaf insects, it feeds on leaves while well-hidden from predators.

    Gray's twig is one of roughly 3,000 insects of the order Phasmatodea, named for the Greek word phasma, meaning phantom or apparition. These stick and leaf insects are found on all continents except Antarctica. They protect themselves by blending into their surroundings, camouflaged through both appearance and behavior. Gray’s twig has the coloration and shape of a eucalyptus stem, and when threatened, it will either be perfectly still or sway as if blowing in the wind.

    Gray’s twig is parthenogenetic, meaning the female does not need to mate in order to lay eggs and reproduce. Males are able to mate with other species, which can create new species.

    The female Gray’s twig flicks its tiny (3 millimeters [0.12 inches]) oval-shaped eggs, which look like plant seeds, onto the soil below the tree. Each egg has a knob called the capitulum, which attracts ants that carry the egg to their nest. Here the ants feed on the tiny knob, while the rest of the egg remains intact, protected until the nymph emerges. The nymph closely resembles an ant, and it eventually emerges from the nest and climbs high into a tree. With metamorphosis, it gradually changes to become an adult Gray’s twig.

    The male Gray’s twig has full wings and can fly, and it is smaller and more slender than the female, which has smaller wings.

    1. What does being parthenogenetic mean for Gray’s twig?

      The females do not need to mate in order to lay eggs and reproduce.

    2. What adaptations help the Gray’s twig egg and offspring to survive?

      The eggs of the Gray’s twig look like tiny seeds, which the mothers drop in a variety of places for a higher chance of survival. Also, each of these tiny eggs has a knob that attracts ants, which carry the egg to their nests. Ants eat the knob but leave the egg, which then grows protected in the nest. The stick insects have no need to protect the eggs−the ants do it for them!

    3. What feeds on stick insects?

      A lot of stick insects are nocturnal, or active at night, to help avoid diurnal (daytime) predators, such as birds, reptiles, spiders, and primates. Bats, however, are also nocturnal and will feast on stick insects, along with many other kinds of bugs. Bats do not need to see their prey, but instead use echolocation to determine where insects are. In this way bats help keep stick insect populations−and other insects as well−in check, maintaining balance in the ecosystem. Otherwise, stick insect infestations could lead to decimated trees and forests.

  • Term Part of Speech Definition Encyclopedic Entry
    camouflage Noun

    tactic that organisms use to disguise their appearance, usually to blend in with their surroundings.

    Encyclopedic Entry: camouflage
    capitulum Noun

    knob-like, terminal structure.

    eucalyptus Noun

    tree native to Oceania.

    metamorphosis Noun

    complete change in form and structure from one part of the life cycle to the next, such as caterpillar to pupa, and pupa to butterfly.

    nymph Noun

    mythological spirit or deity associated with an aspect of the natural landscape, such as a river or forest.

    parthenogenesis Noun

    method of reproduction in which the organism develops a female gamete without fertilization. Common among plants and invertebrates.

    phasmatodea Noun

    order of stick and leaf insects known for their camouflage.

    predator Noun

    animal that hunts other animals for food.

    reproduce Verb

    to create offspring, by sexual or asexual means.