By Jonathon Howard
It’s a dark moonless night and a male moth is out searching the neighbourhood. Although its dark, the moth does not need his eyes for this search. He uses his antenna.
He picks up a scent. It’s a girl. He immediately turns towards the scent and flies towards it.
The scent gets stronger. But as he closes in to meet his new partner: WHAM!
He is caught like a fish on a hook and cannot escape. His life is over as the spider hauls him in.
It may sound sad for the moth. But Bolas spiders hunt by deceiving their prey.
Bolas spiders are not orb weavers. Instead, they present a sticky ball suspended on the end of a single thread of web. To hunt, the spider hangs from the edge of a leaf or twig on a short silk thread.
The spider then begins to emit an odour that smells like a female moth. When a male moth is lured in, the spider swings its bolas. It hits and sticks to the moth and the moth is hauled in. It is like fishing with a blob of glue.
The moth, out searching for a promise, has been caught in a lie. Perhaps that is why the scientific name for bolas spiders is “Celaenia” which means “cruel and grasping”.
But Bolas spiders are a group of spiders whose lives are full of other lies.
For example, some species lay egg sacs that mimic the various plant parts in which they are nestled. It means the eggs are easily overlooked by predators.
One of our local species is a master of deception. Celaenia excavata is a large spider with distinctive brown, white, and black colours that sits in a huddled resting posture during the day. The egg sacs are also large, marbled brown coloured balls, each about 12 mm in diameter. Both the appearance of the adults and the eggs is why the spider has the common name: “bird dropping spider”.
Next time you are out in the bush or orchard, look amongst the scrubby vegetation. You might find one of these Bolas spider trying to hide. Indeed, I stumbled across one on my kurrajongs the other day. I thought it ‘bad’ that a spider’s web had caught balls of bird poop and went to fix it.
Only to find that I, like that male moth, had been told a lie once again.