Thursday, 21 September 2017

A Nice Addition to the Garden

We have been watching this large Nephila sp perch in her web near our porch. She is a very poor web builder and it surprising she catches anything.  The web is seldom intact and there are usually gaping holes in it. The web is typical spiderweb colour, not yellow as in other members of the genus. She measures approximately 40 mm in body length, about 140 mm from the end of one outstretched leg diagonally to another. We try to avoid drawing attention to her during the day as the Black Butcherbird would have her for sure if he detected there was something edible there. They routinely look for these spiders during the autumn of the year when food is a bit scarce.

An unexpected part of the biology of these large spiders is that the female must come to ground to lay her eggs. This is probably most hazardous time of her life since she would be exposed to all sorts of predators, the worst of which is the introduced Cane Toad, Bufo marinus. (I'm an oldie and use the old generic name!!)

 Those red dots are Small Thief Spiders, Argyrodes miniaceus. We counted 20 of them.
Argyrodes minaceus, the Small Thief Spider.

We wish Mrs Nephila success in avoiding the Butcherbird!
There are about 4000 described spider species in Australia but it is estimated that there may be as many as 20,000 species once they are all described, Whyte and Anderson, 2017.

Both "Budak" and Martyn Roninson have commented that the red spiders are actually Pirate Spiders. Martyn further notes that it is the genus Argyrodes. A check in the book noted below indicates it is the Small Thief Spider, A. miniaceus. Martyn further notes that these spiders can steal the prey of the host spider and eventually cause the big spider to abandon its web and seek a new site. And that's exactly what must have happened as she is now not in her web.

Whyte, R., Anderson, G. 2017. A Field Guide to Spiders of Australia. CSIRO Publishing, 445 Pp.


budak said...

the small 'males' with the angular abdomens (real males have longish abdomens) are kleptoparasitic Argyrodes spiders

Mr. Smiley said...

Thanks for your comment. The red spiders are largely gone now and the female has not tended her web for 3 days.
D Rentz