neil

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.

For the sake of appearance, colour can make a world of difference. In tropical rainforests, a bright upper canopy, rich in blue and UV, and a dark understorey, rich in green and orange, contrasts two distinct light environments.

When discretion is important, bright greens blend better in the upper canopy, whereas dark browns have the advantage in the understorey.

When advertising an invitation to treat, as it were, bright blues glow advantageously in the upper canopy, whilst yellow and red signals optimise conspicuousness in understorey. The Hairy Red Pittosporum P. rubiginosum ssp. Wingii, of Australia’s tropical rainforests, is an excellent example of the latter.

I must confess that I really can’t remember when I first came to believe that Green Tree Ants, presented in the previous entry, farmed aphids concealed under frass. However, I am always willing to learn, so thank you Jennifer for the correction.

Under higher magnification a cotton-like covering becomes more apparent, which reminded me of another image I captured several nights ago of what looks like the Psyllids or jumping plant lice that tamborineman mentioned in the previous thread.

In matters of antennae, I imagine that surface area correlates with sensitivity. The male Hercules Moth Coscinocera Hercules must find his mate within a very short timeframe.

Adult females emerge from the chrysalis without mouth-parts, her 4-5 day life does not include feeding. After she emerges and her wings unfold and dry, she emits pheromones to attract a male. After mating, she will fly away, lay her eggs on the underside of the leaves of a food plant and die shortly after.

Funny, the things that you see in nature, like this humanoid face on the cephalothorax of a golden orb-weaver, Nephila pilipes.

I have previously described aspects of this spectacular species of spider, here and here. With this instalment, the adult female in the image below descended from her web on the 19th April to build her egg-sac on the ceramic-tiled floor of our living room.

At the outset, her abdomen was rotund, perhaps twice the diameter of the largest aspect within the image captured at the conclusion of the construction.

On a foundation bed of the same orange silk that can be seen, a white disk was established and then encased in more of the orange material. Five weeks later, the orange casing had lifted. The white disc had been abandoned, but its character was surprisingly hard; rather like coral in its chalky-porousness. I can only imagine that it was produced in much the same way as a mantid’s ootheca – soft upon release but hardened under external exposure.

It had been my understanding that egg-laying was the final phase in the three-month life-cycle of this species, but this individual struggled back to the ceiling and over a succession of days manged to rebuild a small web. Aided by the sympathies of my children, a number of march flies allowed for a fuller recovery and the re-establishment of a master-web. She lived another month and then presumably underwent a second and final reproductive cycle.