Wednesday, October 31, 2012

Ant-mimicking katydid

This small katydid nymph turned up in our yard earlier this month. It was on a plant frequented by Black rattle ants (Polyrhachis australis) which are about the same size as the nymph.




Not only does the nymph resemble the ants at a glance, its movements were very ant-like. Katydid specialist David Rentz thinks the nymph may be Kurandoptera purpura.

Wednesday, October 17, 2012

Peppermint twist

 
Megacrania batesii is known as the Peppermint stick insect for a very good reason. As a defence it sprays a dual-streamed blast of peppermint scented liquid at its predators. The defensive chemical is produced by glands in the thorax and liquid is stored in sacs which lead to ducts just behind the insect's head.  
Megacrania batesii discharging the defensive chemical from ducts just behind the head.
  
 Like all phasmids, Megacrania batesii sheds its exoskeleton in order to grow. The process is practically the same at the sequence pictured in the previous post featuring Phyllium monteithi. The exuvia left behind is typical with one exception; it contains the sacs in which the peppermint scented defensive fluid is found. The result is that the insect is not only soft and vulnerable immediately after moulting, but has to replenish the chemical before being able to defend itself fully. This period is obviously one of hightened risk for this species, and perhaps there are some behavioural modifications during this period to reduce the risk of predation. Species such as the Peruvian stick insect Oreophoetes peruana have a similar defence yet do not shed the lining to the sacs, hence retaining their defensive ability post moult.
 
The entire exuvia with the two white sacs present at the left near the head.

The sacs can be clearly seen filled with the white peppermint scented chemical.