Did you know that all spiders produce silk, but not all spiders make webs? It is this that divides spiders into two groups: weavers and hunters. Generally, web builders are poor sighted and wait for their prey to come to them. The hunting spiders rely on speed and relatively good eyesight to capture prey.
It’s among these hunters that some of the most extraordinary powers are most evident. But the web builders have the power of one of nature’s strongest bio-materials, to build their homes and trap their prey – silk.
This silk is incredibly thin, and finer than a strand of human hair; yet its strength is five times stronger than steel. In fact, it’s almost as strong as the strongest man-made substance, Kevlar®, the material used to make bullet-proof vests.
Body Parts and Functions
1. Brain – A jumping spider’s brain volume relative to its body size is proportionate to ours. As spiders get smaller, the proportion changes. Tiny spiders, in the range of 0.56mm long, have such huge brains for their body sizes that the organs can spill into the animals’ body cavities, and even their legs!
2. Eyes – Which provide surround vision. Most spiders have eight eyes, but there are many different configurations. Jumping spiders have the best eyesight in the spider world. With their eyes positioned around their head, they possess near 360 degree vision, surpassing that of humans. They also have extra wide colour vision.
3. Jaws – A spider’s primary weapon is its jointed jaws (chelicerae) housing two sharp fangs in front of its mouth. Usually only revealed as it bites, venom is squeezed out of the fangs injecting its prey with a neurotoxin found to contain over 1000 chemicals. This kills or paralyses the prey making it safe for the spider to feed on it without the risk of a struggle.
4. Limbs – These hydraulic limbs possess a force that enables a jumping spider to leap up to 50 times its body length, a force that comes almost entirely from its back legs, caused by the body pumping blood into them. It attaches a dragline/safety line of silk onto the surface it’s jumping off to stabilise itself mid-air and control its landing as it pounces on unsuspecting prey.
5. Hairs – These serve as a sensory organ, and are 100 times more sensitive than our best sensory organ, our eyes. Three types of hair on their legs are used to taste, hear and feel. Hearing hairs delicately pivot and move even if a fly buzzes by a few metres away. Touching hairs trigger a quick response if they touch prey. This scanning electron micrograph shows the hairs in detail.
Some Quick Facts About Spiders
1. Jumping spiders can leap 50 times their body length, equivalent to a human leaping across a football pitch!
2. Spiders can run up to 70 times their body length, which is 10 times faster than Usain Bolt!
3. I bet you have heard this before, that a pencil-thick size of spider web can stop a Boeing 747 – one of the largest airplanes in the world – and in full flight too!
4. Spiders can carry up to 170 times their body weight when walking across a ceiling, equivalent to a human carrying a double decker bus
From BBCiWonder
