An Ancient Mimic

stick insectI’m deep in edits for my upcoming novel, Journey’s End, which will be out with Penguin Random House at the end of May. Taking regular walks is a must, to clear my head, and it’s always a treat for me to find an insect like this one during my wanderings – Ctenomorphodes chronus.

Phasmids (or stick insects) are remarkable animals. Even the name, Phasmid, has an evocative, romantic ring to it. They have been disguising themselves as walking leaves and twigs for 126 million years, even before the evolution of flowering plants. C. chronus has an uncanny resemblance to a gum tree twig and can grow up to 18 cm in length. The males are long and slender, have full wings and can fly. The females are larger but their small wings are not functional, except to flash at predators. Phasmids are harmless herbivores, eating gum and wattle leaves. They also eat blackberry leaves, and I sometimes find them doing a good job feeding on clumps of this invasive weed. They often rock back and forth, as if swaying in the breeze.

Stick Insect fossilFossil discoveries from modern-day Mongolia mark some of the earliest examples of twig-mimicking insects. Evolution quickly produced disguises for bugs, with the arrival of the earliest birds and mammals, which visually preyed upon insects during the age of dinosaurs. This is more tantalizing evidence of early insect-plant co evolution. These ancient phasmids were about 7 cm long from tail to antenna tip. They had parallel black lines running along their wings, which at rest would have resembled a ginkgo tree leaf, also preserved as fossils in China and Mongolia where the insects lived.

Spiny Leaf Insect

Spiny Leaf Insect

One especially interesting Australian phasmid is the Spiny Leaf Insect. Females lay eggs resembling seeds, flicking them onto the ground below their tree. The eggs have a knob, called a capitulum, which is tasty to ants. Ants carry the eggs underground, eat only the knob, and leave the rest of the egg in the nest, protected from other animals that might eat it. The young phasmids (or nymphs) hatch after 1-3 years underground They look and behave like ants. When they emerge from the nest they climb into the trees, where they moult into slow-moving leaf mimics.

Phasmids are parthenogenic, which means the females can lay fertile eggs without mating, but the babies will all be girls. Males can even mate with species other than their own, which can create new species. What fascinating creatures! No wonder they’re becoming popular as pets. Museum Victoria is currently breeding rare giant stick insects, that can grow more than 50 cm in length. Next time I’m in Melbourne, I plan to meet these miracle babies!

Congratulations to Womblywoo for winning the prize draw book giveaway! I shall email you soon for your postal address. 

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