Avid readers (surely there are one or two of you out there…) might remember that I promised one day I would write a post on a certain spider. Well, that day has come.
I’ve written up on most of Japan’s large web spinners – jorogumo and onigumo spring to mind. This time I’ve managed to get some reasonable shots of the other major orb weaver – Argiope amoena.
This spider seems to lack a common name in English, so I’ll use the local name koganegumo (黄金蜘蛛) here.
This spider belongs to the same genus as the wasp spider (A. bruennichi) and the St. Andrew’s cross spiders (A. keyserlingi and A. aetherea), to which it bears a strong resemblance. Like its close relatives, the female spins a web with some kind of stabilimentum, or web decoration, and sits in the middle of the web, head downward, and the legs stretched out into an X shape.
Look what I just found! The legs are held out into an X shape, and you can see the web decoration.
The shape of the stabilimentum varies between individuals, but is typically a combination of one to four / and \ patterns extending from the centre of the web. The best known is the X-shaped combination. The exact function of the stabilimentum is unknown, although research suggests that it reflects ultraviolet light which attracts prey insects.
A clearer view of the stabilimentum.
The female koganegumo grows to just under 20 mm in body length, and has a wide abdomen. The abdomen is decorated with wide horizontal gold and brown bands. The male grows to a mere one fifth that size and is typically a dull brown.
It is found throughout Japan minus Hokkaido, and its range also includes the Korean peninsula, Taiwan, and parts of China. Apparently, however, it is quite rare here in Saitama and is listed as an endangered species on a prefectural level!
This spider has a number of regional names, some of which are shared with the jorogumo. (Actually, a lot of people are actually unaware of the differences between the two – they tend to lump spiders into a single category, usually a visceral conglomerate of fear and disgust)
Like their close relatives, these spiders have a single year life span, with males mating once or twice – they never survive a second mating – and eggs are laid in summer. The hatchling spiders survive over winter, but the adults die during autumn.
Larger than life. Actually, she’s quite a pretty spider, don’t you think?
While not embedded deeply in folklore like the jorogumo, the koganegumo used to play a part in children’s games – its web was used to catch cicadas.
Furthermore, there is a tradition of pitting female spiders against each other in the old Satsuma fief in modern Kagoshima.
Apparently, this was started in 1592 by Yoshihiro Shimazu, lord of Kagoshima, as a means of instilling fighting spirit among his men. The event continues to be held today and is designated an important cultural event.
The spiders are deprived of food for three days before the fight. They are placed on a horizontal stick and forced to encounter. The winner is the spider which forces its opponent to fall, starts to wrap it in silk, or succeeds in biting its foe.
It seems that intervention prevents arachnidian deaths.
As seen on NHK news…
I’m sure you’ll agree that the koganegumo is a fascinating and beautiful spider.