Giant prickly stick insect

Description

Extatosoma tiaratum, commonly known as the spiny leaf insect, the giant prickly stick insect, Macleay's spectre, or the Australian walking stick, is a large species of Australian stick insect endemic to Australia. The species has the Phasmid Study Group number PSG9. E. tiaratum is native to Queensland and New South Wales but has extralimital distribution as far away as New Guinea. Female adult E. tiaratum are covered with thorn-like spikes for defense and camouflage. Their long, rounded bodies grow to about 20 cm long. The females are further described as "heavy-bodied, brachypterous and having numerous spines and integumental expansions on the face and legs, including a tuft of spines on the conical occiput of the hypognathous head". As mentioned, the wings of the female are too small for flying, especially when she is gravid. Exhibiting the sexual dimorphism of many similar insects (particularly other phasmids as well as mantises), males are small and thinner, growing only about 11 cm in length and have three ocelli. Males lack the thorny growths except for spikes around their faces. They have long wings and are good flyers who readily take to the air if disturbed or in search of females. Both sexes, when threatened, adopt a threat pose, standing on the front and middle legs, pointing their abdomen up or to the side in a sort of "scorpion" pose. They fold back their legs to defend themselves if anything comes in contact with their abdomen; the pincer movement with the sharp spines on the rear legs can puncture human skin. Adults make clicking sounds and can release a defensive odor reminiscent of toffee. Males may attempt to startle predators by flashing their wings open. E. tiaratum makes use of both passive and active camouflage. It adopts a curved pose when it hangs inverted amongst foliage with "its highly procryptic abdomen curled over its back." Individual E. tiaratum vary in color and appear brown, mottled brown, green, reddish, cream, yellowish, or entirely white. Like many stick insects, E. tiaratum actively sways back and forth or side to side when disturbed or when there is a gust of wind, with a frequency distribution like foliage rustling in the wind. The swaying behaviour may be motion crypsis, preventing detection by predators, or motion masquerade, promoting misclassification (as something other than prey), or a combination of the two.