When I first spotted this messy web, I could barely make out the spider. In its own right, it was tiny; a mere 3-4 mm long, but in the circumstances of its concealment, it was marvellously blended into the broader clutter of debris, at the centre of the stabilimentum (conspicuous feature of silk).
Under higher magnification, an enlarged, multi-coloured abdomen, together with a strategic positioning of legs, concealed the bulk of the spider’s cephalothorax. Upon closer scrutiny, its eyes were just distinguishable between its legs.
It turned out to be a species of Cyclosa, renowned for adding prey remains and other debris to their orb-webs. The function of silk decorations is generally associated with defensive strategies, but there is also a notion that it may increase attractiveness to prey.
In my research of Cyclosa, I read that, under threat, the spiders may vibrate the web, bringing motion to the detritus and in so doing, give an impression of a more expansive population.
I also read the abstracts of two independent studies, which seemed to contradict the findings of each other. One showed no significant tendency in attraction to webs with a stabilimentum, whilst the other revealed 150% more insects trapped than for undecorated webs. Both studies agreed that without detritus columns and silk decorations, spiders were attacked at a higher frequency.
Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.
These very cluttered webs full of insect debris often have the unintended? consequence of catching the predator i.e. small birds such as honeyeaters, thornbills, pardelotes etc that burrow into them looking for food and end up enmeshed.
Bit like catching a fish and finding a raptors claws in it’s back.
The spider probably dined on the bird but the fish was probably relieved when the raptor just rotted away.