Leaf and stick insects

Masters of camouflage, leaf and stick insects are a challenge to find in the rainforest but they are impressive and amazing once found.

Leaf insects hang from the underside of leaves in the trees and might look like a dried dead leaf at first. They can be very large - up to 25cm - but most are about 10 to 14 centimetres. They tend to change their colour according to where they are, so leaf insects can range from pale green to dark brown or they can be blotched to simulate lichen on a tree trunk, for example.

Stick insects (also known as phasmatids) are more diverse and range in size from 10cm to a recently discovered giant stick insect which measured 52cm! While most species are a drab colour, there is one stick insect from the Wet Tropics rainforests which is a stunning sky blue.


Stick insects

Most species of stick insects live in the trees, feed on the leaves and look just like a branch. The easiest way to pinpoint one is to look for a branch that seems out of alignment to the other branches or a branch that appears to be attached to the outside edges of leaves.

The female's body is much larger than the male's and both have wings - but the males' wings are larger. Females don't travel around much and emit a hormonal perfume (called a pheromone) to attract the males to them for breeding. The males have larger wings to enable them to fly longer distances in search of females.

Although the stick insects are well camouflaged to aid their invisibility to predators such as birds, their wings provide a backup defence system. Normally, their wings fold up very neatly along the body but the stick insect can spring the wings out suddenly. The colours of stick insect wings can be vivid colours which can startle a potential predator momentarily - just long enough to enable the stick insect to fly away.


The peppermint stick insect

The peppermint stick insect (Megacrania batesii) has a very small and patchy distribution along some beach areas in Cape Tribulation, Innisfail and Mission Beach. It feeds only on a few species of pandanus and these spikey-leaved palms also provide some shelter from predators. The peppermint stick insect spends all its time on the pandanus leaf, feeding, sheltering, mating and laying its eggs on the leaves where they roll down to the tight-fitting leaf axil to 'incubate'. Why is it called the peppermint stick insect? As a defense mechanism, it sprays an irritating fluid at any predators (which include curious tourists) and this fluid smells like peppermint. This is a strenuous act for the frightened stick insect so, if you are lucky enough to find one in your travels through the Wet Tropics, please don't try to touch it.

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