Titan Stick Insect, the Longest Insect - Acrophylla titan
This page contains pictures and information about the Titan Stick Insects that we found in the Brisbane area, Queensland, Australia.
Titans are in the family PHASMATIDAE, order Phasmatodea. The insects in this order are large to very large. This order includes the Stick insects and Leaf insects. They tend to resemble sticks and twigs, usually they are green or brown in colour. They spend much of their time hanging motionless in plants. Even if they move, they swaying slightly as if wind movement. They are not easily seen for their heavily camouflage. Stick insects have powerful mandibles. They are herbivorous, they eat plants only. Titans feed on leaves of cypress trees. But they also feed on eucalyptus in captivity. As most of other stick insects, Titan females are larger than male. The males are good flier but the females are poor fliers.
Searching for Titan
We know there should be the Titan Stick Insect in Brisbane area. However, besides in the Museum, we never seen any Titan adult in the wild. We found nymph which look like Titan but it is not so sure for a nymph is harder to be identified. We tried to raise this nymph to adult but not success. From Paul Brock's information Titan's food plants is 'Bribie Island Pine', so every time we go for bush walking, if we met trees look like a 'Bribie Island Pine', we will stop and look for Titan for a few minutes. But so far with out any luck.
One day (late winter) after lunch, as usual, I went for a walk near my office. Along a quiet street in Yeerongpilly, I saw hundreds of ants attending something on the ground. I thought it could be a dead worm. Come closer and I found that it was a stick, and was moving. I drove away the ants and saw a 20cm insects, still alive. I carefully took it home but it dead a day later. I think it must be the Titan, however, its antennae were missing, its wings were broken and only the base part were leave. Its body and legs are extremely soft and with some moulting skin still attached with it. So I think it must be fallen down when moulting and attacked by ants. This should be its last stage of moulting because there was the wings.
At least we found a Titan and know that the insects will do the last moulting in late winter. Any we can still find Titan in Brisbane.
I think to myself, if there is the Titan on the ground, it must come form some where on the tree. There could be some other Titans. So I went back to the street on the next days and recognized three cypress pine trees. I spent tens of minutes on each tree and, yes, I found two Titans on two trees.
One Titan is about 22cm in body length, fully winged and should be the female adult. The other one is 20cm in body length, with wing buds and should be the last stage instars. It was feeding on the on the pine leaf. They are about two meters about ground. I took the instars home and watch its growth.
The Female Titan Stick Insect
The Male Titan Stick Insect
From Nymph to Adult
I find one Titan larva which is about the size of an adults but its wings are still not developed. I know this must be the last instars and I take it home and watch its grow.
Stick insects will undergo some molting stages. After each molt, they will usually eat their exuviae.
Questions for Discussion
Why the Titan Stick Insects are so big?
Stick insects are large in size in general. One reason is they mimic a stick to hide away from their predators, usually birds or some other larger sized vertebrae animal. The camouflage will only effective to cheat larger predators. To smaller size predators such as spiders and praying mantis, sticks insect may not look like a stick. One of the solution to avoid those smaller predators is larger in size. This also explained why some stick insect mimic ants and not stick when they are in small larva stages.
For Titan Stick Insects, there may be many factors make them the longest insects. I notice one major factor which is theirs hugeness resemble the size of the stick on the tree that they feed on. They feed on the cypress trees. For those trees, beside some main trunks, most of the branches are about the size of the Titan's body. There are many branches in high density. If a twig fall from the top part of the tree, it usually hangs in the middle of the trees. When I look up from the bottom, I saw high density branches, live of dead, close together. There could be many Titan or none, very hard to tell. Titans mimic the size as well as the shade of the branches.
Also when I disturbed the stick insects, one of the defence mechanism I noticed was they try to put their front pair of legs straight in front of their head and make themselves look as large as possible. So I think hugeness is also one of their survival factors.
See us in our Home page. Download large pictures in our
web page. Send email
to us. A great way to support
us is to buy the CD from us.