Friday, January 29, 2010

The two-tail spider

Spiders are very cryptic. They somehow can blend with their surroundings in such a manner that very often the human observer will not notice one just right in front. Even as a spider hunter, I suppose that I manage to notice less than 50% of spiders that I encounter in any outing. This is because spiders tend to have a very good integrated camouflage tactics which involves colors, patters, body position and locomotion. One of the masters of camouflage is those from the Hersiliidae family which are also known as the two-tailed spiders.

The name was derived from the extremely long pair of spinnerets protruding from the back side. They are so long that sometimes the look longer than the entire body itself, which makes them look ridiculous since an animal with two tails can hardly register in anyone’s common sense. The remarkable tactic employed by the hersiliid is by having a flat body and the tendency to press itself to the surface, hence almost eliminating the shadow casted by natural light. They also seem to have a tendency to lie on a surface with patterns and colors matching their body. Some other spiders such as the huntsman Pandercetes sp. has very similar camouflage tactics and herlisiid can be distinguished by the long spinnerets and the fact that its third pair of legs is much shorter than the rest.

Close up of a hersiliid.

For those not familiar with the anatomy of spiders, the term spinneret refers to the organ there the silk thread emerges from. These things look like small segmented organs protruding at the bottom backside of the abdomen. Depending of the families, spiders may have up to 4 pairs of spinnerets weaving different kind of silk. Each spinneret is attached to a specific type of silk gland which secretes different kind of silk, for example, for making cocoon, drag line, sperm web or axial thread in webs.

One note about the two-tail spider is on its hunting habit. Mostly they hunt day and night by ambush. Due to its cryptic nature, the spider can lie on wood or rock until a potential prey arrives. It will pin the prey to the surface with its two long spinnerets and than rotates around the prey while spinning silk around it. I have never personally seen this but it is entertaining to imagine a spider doing a merry-go-round for a living.

A hersiliid found on a tree trunk in a primary forest. Note the shorter legs III.

This spider can be found in primary and secondary forest, sometimes in human habitat as well. It is not commonly seen mainly due to its extremely cryptic nature but once you have an experience identifying it, finding another would be much easier. A good thing is that this is among the few spiders where males and females are of almost equal size and appearance.

A small hersiliid who chose a painted brick wall as habitat. Some how it seems to work well.

We have four genera in South East Asia: Hersilia, Murricia, Neotama and Tama. Hersilia is mainly a tropical genus with many species recorded in Malaysia. Just in 2004 two Brazilian arachnologists described 4 new species of Hersiliidae found in Kinabalu National Park and about 10 years before that over 20 species were described in South East Asia and South Asia. Such many recent discoveries might suggest that there could be more hersiliid species yet uncovered in our region.

1 comment:

  1. Thanks for your visit and information.
    Will certainly come back for more information.