Monday, August 27, 2007

X-Spider Girl

I have an Argiope Lobata in my yard! Its ancestors dwell around the Mediterranean and the Iberian peninsula. Of course, we have everything in Miami, so why not her too? It's a her and I know for sure. Here is a tidbit I dug out for you:

Accurate identification of spiders often requires examination of reproductive organs and other minute structures under a binocular microscope (20x-80x) I bet you didn't know that, right? You will need to distinguish between male and female spiders. Whereas the palps of females and immature males are leg-like, each palp of a mature male is usually swollen at its terminal segment and is equipped with some complex structures where the semen is stored and subsequently discharged when it is inserted into the genital opening of the female during mating. The genital opening of the female is located on the underside of the abdomen just in front of the epigastric groove. The position is often indicated by a hardened (sclerotised) structure called the epigyne. The epigyne may come in the form of a simple or complicated pit, plate or hook.

If this completely stumped you, learn about spider body parts at this excellent page. If you click on the photo to see it in high resolution, you can distinguish parts of the legs, which, from the tip, are: Tarsus, metatarsus, tibia, patella and femur.

Argiope spiders make orb webs which are suspended vertically 1-2 metres from the ground. The web of mature female spiders of this genus can be easily recognised by the X-shaped zigzag bands of white silk in the centre of the web. The brilliantly colored spider with silvery hair on the carapace sits head down in the centre of the web, and holds its legs in pairs in such a way that they appear to be aligned to the four arms of the letter 'X'.

The males are dull in colour, much smaller and like the females, have the habit of pairing their legs. Their webs are, however, decorated by a lace-like centre, instead of white bands in the shape of the letter 'X'. So, definitely, my lady orb weaver is an established female. I'll call her "X-Spider Girl," and hope she'll hang around for a while.

Argiope Lobata


Ann (MobayDP) said...

Very interesting information there Lan.
I must admit though that I doubt I will ever get close enough to a spider to determine its gender!

laurel said...

I have often wondered about these spiders. They are so unusual looking.

Thanks for doing the research for us!