Thursday, May 26, 2011

Elusive Arachnids

After years of looking and hoping I have finally encountered some Australian Amblypygi. This group of bizarre looking arachnids are known as ‘whip spiders’. They superficially resemble true spiders but are very different in many ways. Australia has a handful of species in the tropics, but they are neither common nor easy to find.

Charinus pescotti from Kuranda
Amblypygids are found throughout the world, primarily within tropical and subtropical habitats. Australian Amblypygids are relatively small compared to some of their overseas relatives. This species Charinus pescotti only grows to a body length of around 10mm, with a leg span of around 25mm. The giant African Euphrynichus amanica can attain a leg span of up to 400mm.

Amblypygids have two distinct body parts and four pairs of legs, so at a glance they are a little spider-like, but that is where the similarity ends. The abdomen is flattened and has 12 segments, and they lack spinnerets and cannot produce silk. The first pair of legs are antenniform; very long and delicate compared to the other legs, and extremely sensitive to chemical and vibrational cues.

The first pair of legs are antenniform and are important sensory tools.

One of the most striking features of these animals are the palps. They are raptorial; they have become adaptations to snatch and impale their prey with. The palps have rows of spines on the inner edges, and while not in use the palps are tucked up in front of the face giving them a fearsome appearance. The chelicerae (mouth parts) are fang-like and are similar to those of mygalomorph spiders, but Amblypygids lack venom. Prey, usually insects, is captured with a lighting fast strike using the palps. The animal is the drawn back to the front of the Amblypygid where the chelicerae begin to tear it open while digestive juices are expelled into the opening. The resultant semi-digested fluids are sucked back up in the same manner as spiders do.

The spiny raptorial palps are held in front of the face when not in use.

Monday, May 23, 2011

A true leaf insect

For those interested in Australian phasmids there are several species on the must see list. Up there would be such species as the Lord Howe Island Stick Insect (which was considered extinct until 2002 when it was rediscovered on Balls Pyramid, a small rocky outcrop off the coast of Lord Howe Island. Another on the list would be the true Australian Leaf Insect (Phyllium monteithi). This species is known from only a handful of male specimens, which have been found between Innisfail and Mossman. A female was photographed in the Cairns Botanic Gardens, but the specimen was not collected. Recently we were lucky enough to encounter a live male which turned up on David Rentz's light sheet.

Leaf Insects are truly masters of disguise, both sexes are broad and flattened like leaves as juveniles, but only the female remains so as an adult. They are believed to be canopy dwellers which explains the lack of encounters, and may feed on the foliage of Cryptocarya mackinnoniana. They will also feed upon Guava which this specimen certainly did. When we first moved to Kuranda we planted several Guava trees just in the hope of attracting these illusive insects.

The genus Phyllium is represented by over 30 species throughout southern Asia. The biggest, Phyllium giganteum is a common representative within live insects displays around the world. They are also commonly kept by insect enthusiasts throughout Europe and the USA.

The mature male Phyllium monteithi. Males have fully functional wings and are excellent flyers.

Peeking over a leaf - note the extremely hairy antennae.

The underside of the abdomen reveals the segments hidden by the wings when viewed from above.

This specimen readily fed upon Guava, one reason we inspect all Guava trees we see with great interest.

A close-up of the male feeding.

While most male phasmids have some flight capability, this one would readlily take to the air and was quite agile on the wing.