No group of animals continuously astonishes me quite like the spiders. Sure, they’re terrifying, but they are also some of the most ingenious animals in the world. The sheer amount of creativity spiders use to catch different prey and survive in different environments amazes me. One such group of spiders is the bolas spiders, named for their unique way of catching prey.

The bolas spiders are members of the ‘tribe’ Mastophoreae, which is composed of three genera: Cladomelea, Mastophora, and Ordgarius. They live mostly in the Southern Hemisphere, in Australasia, Africa and America. These species live in a wide variety of habitats, that have one thing in common: the presence of moths.

Moths, you see, are the main prey of bolas spiders. In fact, these clever spiders devised their complex hunting technique purely to assist in hunting moths. Most spiders cannot catch moths, for when a moth gets stuck in a web, its scales stick to the web, and the moth can still get away. Not so with bolas spiders. They create a special hunting thread, at the end of which is a round droplet of sticky goo, and which is called a bolas. The bolas is a neat little piece of construction, and consists of a tangled mess of stretchy fibres, covered by a thick viscous layer which is itself covered in a low viscosity layer. This faster flowing layer flows over the moth’s scales, and attaches to its cuticle. The thick layer provides support to the bolus, while the stretchy fibres give the spider more range.

A bolas spider dangling its sticky trap, waiting for a poor moth to flutter by.
A bolas spider dangling its sticky trap, waiting for a poor moth to flutter by. Photo Credit: Matt Coors (http://mattcoors.com/)

Of course, bolas spiders aren’t going to leave their survival up to a few chance occurrences of moths flying by at the right time. They produce pheromones that attract the moths to the bolus – each species of spider only produces a few pheromones that are specific to the prey they hunt. These pheromones are so specific that production of them can be time dependent. For example, one species of bolas spider hunts two species of moths, one which is active until 10:30pm, and one that is only active after 11:00pm. The spider produces both pheromones in the early evening to attract the first species of moth, but later at night the spider only makes the second moth’s pheromone, as this species is driven away by the pheromone of the first moth. Pretty crazy stuff.

These spiders have one other important adaptation that enables their survival: defensive mimicry. Many species of bolas spiders look like bird droppings, and this allows them to sit on the top of leaves while resting during the day. Another species looks like a snail that is common in its area, and hides on the underside of leaves where the snails would be found.

A bolas spider, hiding as some bird droppings.
A bolas spider, posing as some bird droppings.

I can’t believe how complex spiders are. Every time I blog about them I get more and more impressed with these arachnids. Hopefully this happens to you every time you read my posts about spiders!

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