Important species of Pontine Islands - Argiope lobata

Important species of Pontine Islands - Argiope lobata

3 December 2020

Among the spiders of the Ponziane, one of the most unmistakable is certainly Argiope lobata (Pallas, 1772), both for the peculiar abdomen lobes (making it easy to distinguish from the more common Argiope bruennichi), and for the structure of the web, very large and with a complex design. The web of these spiders is in fact decorated with a structure called "stabilimentum", that seems to have a specific function in attracting insects and reducing the impacts of birds on the webs.

The male of this species is small (its body does not exceed the length of 6 mm) while the female is definitely larger (it can reach a length of 25 mm) and eye-catching, making it an ideal subject for photographers, also because even if approached it remains stationary in the center of the web, showing off its beauty.

This spider mainly feeds on orthoptera, although it does not disdain other insects that get trapped in its web. If disturbed, with a particular behavior it makes the web vibrate vigorously, in order to discourage a potential predator. Like the congeneric Argiope bruennichi, this species is not dangerous for humans: it is not aggressive and in the rare cases of bite, apart from the pain due to the chelicerae piercing the skin, it only cause local redness that persists based on sensitivity of the bitten subject.

How did such a spider colonize islands such as the Ponziane? Juvenile spiders are capable of using the wind as a dispersion tool: through the so called “ballooning” they are able to be "launched" beyond, for example, a body of water, far away from their place of birth.