As I wandered near a shrub in the garden the other day, I happened to notice a leaf flutter lightly. There was no wind at all at the time, so I had a closer look. So good was the camouflage, it took some time to locate her – I think it was a female, they are much larger than the male. Head to tail she measured 130mm and with her forelegs extended she was well over 200mm. I gently removed her to another location to get some better views, and returned her to where I found her later.
Stick and leaf insects are phasmids. They are herbivorous with simple front legs that do not have the raptorial spines of the carnivorous mantids. The shortened forewings are hardened into tegmina that always cross over right onto left. While I was moving in to take some photos, she suddenly opened her wings to display a bright blue patch. This is apparently explained as a secondary defence behaviour to startle any predators. There are around 150 species of leaf and stick insects in Australia. Their excellent camouflage skills mean we don’t see them very often. Mostly their numbers are quite low, only breeding when conditions are just right. There are three pest species that can reach plague proportions and defoliate large areas of bushland. One of the joys of coming across such a specimen is the following research of the species and discovering many fascinating facts. For example, many phasmids simply drop their eggs to the ground where often they are taken by ants into their nests. Inside the ant nest, part of the egg is eaten by the ants, but the egg remains mostly intact and is safe from attack by parasitic wasps. There is a strong pet trade in stick insects, and probably the rarest insect in the world is the Lord Howe Island Phasmid.