Most people in Northern Australia know Golden Orb Weavers – very large spiders which weave metre-wide webs and are famous for catching birds in them – but not so many know that we have three species. They are closely related, of course, all being in the genus Nephila, and two of them, N. plumipes and N. edulis, are quite difficult to tell apart:
As adults, the females of both species are grey-brown with wavy markings on the underside of the abdomen. They are both large (as spiders go), although N. edulis at 40mm nose-tail can be twice the size of N. plumipes at 19mm. Both tend to leave a messy string of prey debris in their webs. The most positive way of separating them is that N. plumipes has a bright yellow sternum or chest.
The third species, Nephila pilipes (sometimes known as the Northern or Giant Golden Orb Weaver), is much more recognisable. It is slimmer in the body, its legs are longer in proportion, and from beneath it shows bright yellow knee joints and sternum.
This species is the only one I have found in my own garden. Every year or two we have one or two young ones blow in and make themselves at home until age or misadventure removes them. (I’m always delighted to see them, because they are so beautiful. Some other folk are not so enthusiastic, although they are completely harmless.)
Our latest arrivals, who prompted this post but have yet to appear in it, were first spotted on March 30. We lost sight of one three weeks later and the other last week but they were photographed several times before they vanished and will serve to illustrate the rather different colours of juveniles. This one (back/underside) is not much bigger than a St Andrew’s Cross spider and the abdomen is strikingly striped. Six weeks later the yellow highlights underneath are much brighter while the abdomen is almost the adult’s grey-brown on top and the top of the cephalothorax is the adult’s silver.
So much for the females. What of the males?
They are tiny. A particularly striking illustration of the difference is this photo on Arachne.org. (If you scroll up from it you will find one of the famous bird-eating photos.)
Since I have begun linking to other people’s material, here is a fossil Golden Orb Weaver (we now know they have been around for at least 165 million years) and here is Wikipedia’s page which has some pretty off-beat information as well as all the basic facts.