Wednesday, 12 May 2010

The golden orb Weaver; Nephila pilipes

The other day I was tending to my orchids and almost ran head-long into this creature. It's a Golden Orb Weaver, Nephila maculata. We have dealt with this species before in the early days of this blog, but this one was very photogenic and it will be interesting to monitor its progress. That will all depend on its not being discovered by the local Pied Butcherbird which seems to seek these morsels out at the end of the wet season. [Our local resident butcherbird was found dead on the road 2 days ago and I really miss his companionship in the early morning when I check my light sheet.] Golden orb Weavers occur in many places. Check this site to see the variety of body shapes and sizes.

This is a big spider. It measurers 19 cm from the tip of the foreleg to the tip of the hind leg. That's 7.5 inches for you northeners. The web is 1.2 m in diameter. These spiders have been recorded catching small birds, lizards and frogs. Their name comes from colour of the orb--the web. In the sunlight it has a distinctly golden or greenish appearance. It is remarkably strong; you can rest your arm along the top line without breaking the web.
Ventral view. Can you spot the male? It's the tiny fleck at the top in the 12 o'clock position.
This is the dorsal view of the abdomen. The holes are probably for breathing purposes. Note the surface covered in minute hairs.
This is the ventral surface of the abdomen showing a few more openings for the book lungs. Note the pattern. To the left are the spinnerets. Check this link to see how they are used.

The spinnerets have produced a strand of silk even though she is stationary. She has a "lifeline" that keeps her in contact with her web should any catastrophe strike.
With this view of the spider you can plainly see the male of the species. He lives in fear of his life and only to mate. This he must do with great caution as with one false move, she might eat him.
This male has met with some misfortune. Note that one leg is missing and it appears that he is missing one of his pedipalps. These are the modified legs that serve as intromittent organs. He must carefully position one of these legs into the genital opening of the female in order for there to be a successful mating. If she is not in the mood, she will either flick him away or eat him! Simple! I'll keep you informed of his success and the fate of this spider.


Additional Note

My friend Graham Milledge of the Australian Museum, Sydney has pointed out that in 2007 a paper was published by Harvey et al. (2007) on the Australasian Nephila spiders. The species under consideration above is now known as N. pilipes (Fabricius) 1781. This is an extremely old name dating back to the early days of binomial nomenclature. N. maculata Fabricius 1793 is now considered a synonym, that is, it is believed to be the same species and the older name is the one we should now use.

This species has a broad distribution as can be seen from their distribution map. Thanks to Graham for the info.

Reference

Harvey, M. S., Austin, A. D., Adams, M. 2007. The systematics and biology of the spider genus Nephila (Araneae: Nephilidae) of the Australiasian region. Invertebrate Systematics, 21: 407-451.

3 comments:

Camera Trap Codger said...

The late arachno-ethologist Mike Robinson took great pleasure in captivating his audiences with eloquent stories of "spider love" -- complete with mime -- and they culminated of course with the the female's morbid trick.

He was a great fan of Nephila of all stripes, and asked me for specimens of maculata from Burma. I packaged about 6 of them singly in plastic water bottles lashed together as carry on baggage. Unfortunately the specimens weren't the maculata he had hoped for, but a lesser taxon.

That didn't stop him from releasing them in his office (he was then the National Zoo's Director) where they spun large webs -- a conversation piece and a prop for his spider love stories.

randomtruth said...

Amazing shots Dave. I saw them in the Daintree, but didn't have the chutzpah to get close for macros.

I find it entertaining that their scientific name is just 2 letters off from a lovely endemic California wildflower - Nemophila maculata. No relation right? :)

HomeBugGardener said...

I've read that that yellow Nephila silk is the strongest known, and having run into a few webs, I can believe it.

Sorry to hear about your butcher bird, but interesting that they pluck the spiders out of the web. I've always wondered what with the bold, constrasting patterns and the spider sitting so obviously in the web night and day, if the colouring wasn't aposematic and their taste horrible.

But then there is Nephila edulis - which implies someone thought at least this species edible.