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Africa Geographic Travel

Written by Ben Coley (head trainer)

Spider silk has many unique properties, from its strength and durability to its immunity to bacteria and fungus. It is, after all, the strongest substance found in nature. 

There exist a multitude of possibilities within human technology if we could fully synthesise this magical protein from fabrics to biodegradable wound dressings. However, rather than looking at potential uses for it, perhaps the best way to appreciate its unique nature is to view it in the role that it was designed.

Silk is used by spiders in a whole variety of ways but its most diverse use is as a weapon. Everyone knows that webs are used to catch flying insects, but there are many more ways in which spiders have evolved to use their silk to aid in procuring a meal. As part of the Bushwise and FGASA syllabus, students learn about some of these amazing arachnids and if lucky enough, may even witness them in person as our eagle-eyed trainers keep a look out for even the smallest members of this incredibly diverse and resourceful group of animals!

Below is a list of some of these fascinating creatures that have taken their art of war to new extremes:

1. The hackled orb weavers

The family of Uloboridae is the only non-venomous family of spider in the world, yet despite this disability, these spiders possess a rather un-spider-like way of subduing their prey.

When an insect becomes entangled in its web, these spiders are unable to inject any venom and thus resort to completely enveloping its prey in silk. The immense pressure created by this silken shroud is enough to crush the victim to death just like a constrictor would suffocate its meal.

In some cases, a spider will will spend more than an hour mummifying its prey and in doing so, use well over 100 metres of silk! It then regurgitates its digestive enzymes and sucks up the remains, leaving only a hollow silken tomb.

© Robert Whyte/Flickr

2. Net-casting spiders

Also known as ogre-faced spiders, these terrifying looking spiders have developed a very unusual way of using their silk. Rather than spinning a web for the prey to become stuck in, the net-casting spider takes the web to the prey.

It spins a net of silk that it then holds outstretched at the corners with its four front legs and suspends itself above its hunting ground. Its massive eyes pick up movement and in a flash it extends its legs and releases the tension causing the silken net to ensnare its prey.

net-casting spider
© Frank Vassen/Flickr

3. Bolas spiders

This odd looking group of spiders, some of whom mimic bird droppings, use a somewhat wild west-based hunting technique. The spider suspends itself from the underside of vegetation and releases a single strand of silk tipped with a globule of sticky goo.

It then swings this ‘bolas’ around and launches it at moths flying by just like a lasso! If this was not amazing enough, the bolas spider produces species specific pheromones that mimic its prey of choice, thus enticing the moths to within range of its bolas.

bolas spider
© Richard Bradley

4. Buck spoor spiders

The unusual name of this spider refers to the antelope-like imprint in the sand that gives away its presence. The female digs a small impression in the ground and constructs a sheet of silk above her that is camouflaged with sand. She then lays tripwires of silk in a circle around her ambush site and settles down to wait.

She sits with her highly sensitive legs in contact with these trip wires and as soon one is disturbed by its prey she rushes out, snatches her unsuspecting victim and returns it to her lair.

spider trap, sand
© JMK/Wikipedia

5. Spitting spiders

Perhaps the most innovative way of using silk as a weapon has evolved with the spitting spiders. These tiny predators sneak up on their prey and shoot out venom from their fangs to ensnare their meal. The venom is shot out in a zig-zag pattern to ensure that its target is completely enveloped.

The victim, not only glued in place and helpless, then succumbs to the spitting spider’s coup de grâce: The silk is laced with a neurotoxic venom that paralyses the victim allowing the spider to remove its quarry and enjoy its prize in a safe place!

spitting spider, silk
© Robert B. Suter/ Gail E. Stratton
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