This absolutely 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! 

This individual is the longest stick insect I have ever had in my personal collection and she measures 23 cm from her head to the end of her abdomen!  In the wild they live in the Queensland area of Australia and their natural diet is the leaves of Eucalyptus trees.

When she sits with her front legs fully outstretched as in the top picture below she measures a massive 34cm!  Despite being huge, she is not even close to the record for the world's longest stick insect as some species have been recorded in Malaysia which, when outstretched, measure more than 50cm or half a metre!

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.