This huge stick insect is a female of a species with the scientific name ACROPHYLLA WUELFINGI, sometimes known as the giant walking stick or Titan stick insect due to its huge size!  In the wild they live in the Queensland area of Australia and their natural diet is the leaves of Eucalyptus trees.

Despite growing to close to 30cm in length this species is not even close to the record for the world's longest stick insect.  There is a species from Borneo which, when measured with legs fully outstretched, can measure more than 55cm!

The picture below is of a newly hatched Acrophylla wuelfingi on my thumb - as you can see they are truly tiny as newly hatched nymphs! 

It is hard to believe that something so tiny can end up so large, but having seen their development for myself I can honestly say that they do!  They are usually green when they are nymphs, quite different from the adult colouration which comes along later, as shown by the larger nymph below which is still a lovely shade of green like the tiny baby above.

Like many species of stick insects, male Acrophylla wuelfingi are much smaller and more slender than the females as you can see below.  They are also able to fly well as they are much lighter than the females and have well-developed wings.