I was very lucky to come across a sleeping 𝘖𝘳𝘥𝘨𝘢𝘳𝘪𝘶𝘴 𝘩𝘰𝘣𝘴𝘰𝘯𝘪 this week. I almost walked past it, thinking it was a large bird dropping.
But, luckily, I took a closer look and realised it was this remarkable spider. The resemblance to bird droppings is not accidental. Their poo-like appearance is designed to let them rest in the open during the daytime unnoticed by predators. The size of the spider indicates that this one is female as the males are considerably smaller.
Whilst they are from the Araneidae family of orb weavers (and the Cyrtarachninae subfamily) these spiders are from a group known collectively as Bolas or Bolas-using spiders.
𝘖𝘳𝘥𝘨𝘢𝘳𝘪𝘶𝘴 𝘩𝘰𝘣𝘴𝘰𝘯𝘪 are nocturnal spiders and mainly catch moths – for many predators, moths are very difficult to hold onto owing to the slippery and detachable scales on their wings. So, these spiders evolved a niche hunting method much like one used in South America with a Bolas – a rope with weights on either end which is swung around and then flung to tangle the legs of the prey.
The 𝘖. 𝘩𝘰𝘣𝘴𝘰𝘯𝘪 spiders dangle a web thread from their second leg and on the thread they place one or more sticky ‘capture blobs”, which are also scented like female moth pheromones. When they hear a hapless moth approaching, they begin whirling the thread around and when a moth is hit and then caught by the sticky capture blob, they can be hauled up and subdued, much like an angler would cast a line for a fish.
I hope to see this behaviour at night sometime but count myself very lucky to have had a sighting of this spider. The diversity of methods that spiders use to capture prey is quite remarkable and we are so lucky in Hong Kong to have so many of these amazing arthropods.