Monday, 30 April 2018

Nice Cricket, Awful Name

Pseudotrigonidium australis (Chopard), adult male in typical pose

This little cricket was described by Lucien Chopard, a legendary French entomologist in 1955 as Tremellia australis. Fair enough. The name is simple and easy to remember. But in 1999 a Russian entomologist taxonomically massaged the tribe resulting in a lot of splitting. Tremellia was redefined and T. australis did not fit the new concept of Tremellia. So it was transferred to the larger genus Pseudotrigonidium. Further he established subgenera within Pseudotrigonidium, but apparently left the sole Australian example, T. australis, and a couple of other species from Borneo, in neither of the two allotted subgenera. So it becomes Pseudotrigonidium australis (Chopard)- the Kuranda Tree Runner.

In dealing with this taxon for the Guide to Australian Crickets to be published by CSIRO, we had to try and discover what the species really looked like. The type was an old specimen, tattered and discoloured and without precise locality date. Otte and Alexander in their monograph collected some specimens from near Kuranda.

As luck would have it, the species was discovered literally in my own backyard. The living crickets look nothing like the type nor the preserved specimen collected by Otte and Alexander in 1960.
 When viewed closely, the crickets are very colourful with brown and yellow markings seemingly aiding in camouflage.
Even the head is distinctive with stripes and light-coloured patches. In life the eyes have a greenish tinge.
 Pseudotrigonidium australis (Chopard), adult male in typical pose
The crickets have a very distinctive posture. They always are directed downwards, legs askew.They have extremely long antennae and excellent eyesight. The antennae are in constant motion. When disturbed they dart downwards but in a spiral fashion to attempt to confuse the predator. Since they cannot fly, the utilise both their colour pattern as the first line of defence followed by their extremely fast movements.

Males sing from tree trunks after dark. This continues through most of the night into the pre-dawn hours if the weather is warm and not too wet. Adults and nymphs can be found on the same tree trunk. It is interesting that not all trees are inhabited by the crickets. If there is a pattern, the desired trees have furrowed bark and have some growth of lichens. Also the diameter of the tree does not fit a pattern. Trees of 8-9 cm can have crickets as well as those 10 times that diameter. Females supposedly lay their eggs in the cracks in the bark. These crickets occur from the Daintree south to the Kuranda Ranges. We have not found them in the Atherton Tablelands.

1 comment:

Tony Robillard said...

Nice one Dave (and sorry for the awful name.. and subgenera are quite catastrophic I agree), did you manage to record the song as well?