July 14, 2011

Stuff of Nightmares

Spiders have been around for 130 million years. We must all be thankful none of them evolved to the size of a dog.

Of all the creepy crawlies that give people the willies, spiders, those eight legged twin fanged arthropods with their six to eight pairs of eyes would have to be in the top league of nightmares had nature allowed them to grow to the size of a large dog. Fortunately for us nature limited their size to range from that of a pinhead to the 12-inch dinner plate spread of the Goliath Tarantula. As a result few are dangerous to man and the chances of being bitten by one of these is remote. That said if you travel a lot here are five it would be wise to avoid.

The Funnel Web Spider Australia’s most poisonous
The Redback Spider of Australia
The Brown Recluse Spider of the USA
The Black Widow Spider of the USA
The Wandering Spider of Brazil often fatal to children

There is the case of paraplegic David Blancarte who was bitten by a Brown Recluse Spider that brought the nerves of his legs back to life some months later allowing him to walk again. But this is the only recorded case of a beneficial spider bite.

As a rule spider’s prey is restricted to insects though some of the larger varieties are known to feed on frogs, lizards, snails and occasionally small birds. But it is their methods of devouring their meals that comes close to horrific. Being unable to eat solids, spiders predigest their food by injecting digestive fluids from their stomachs directly into the body of their prey to liquefy the inner tissues and organs to a thin soup before sucking them out, reducing the body of the victim to an empty husk in the process. Worse, if not hungry at the time of capture the spider will enmesh its victim in web, paralyse it with venom then leave it fresh and alive until hunger returns.

Mating is a problem for male spiders. Spiders have voracious appetites and the male being much smaller than the female has to approach his love with extreme caution, spending some time stroking her legs until she is sufficiently pliable for him to do his duty. But once sex is completed she usually awakes from her torpor, binds him in web and eats him. But though not around to see it he often has his revenge. After laying around 40 eggs, the Australian female social spider cannot reproduce again. During the summer she collects large insects for her young to feast on while she fattens on the leftovers. But as the young spiders get hungrier, they suck the blood from their unresisting mother's leg joints and when she becomes too weak to move, her young attack her, injecting her with venom and digestive juices before eating her alive.

But like them of hate them the spider has survived for 130 million years and has learnt some pretty nifty tricks along the way. The tensile silk they spin is stronger than steel and so light in weight that a strand to encircle the earth would weigh only 16 ounces and is sufficiently ductile to stretch 40% of its length without breaking. Using their web they are capable of flying or ballooning for hundreds of miles on the wind, controlling their altitude by releasing or reeling in the silk. They have highly tuned sensory hairs on their legs, so sensitive to air currents or low frequency air vibrations they can sense a flying insect and catch it in mid air. In fact we owe them a debt of gratitude for their prodigious taste for insects, as it has been calculated that in the United Kingdom alone the weight of insects eaten by spiders every year exceeds the weight of the population.

Cunning creatures with the mathematical ability to construct an intricate yet perfect web within an hour make them all the more formidable. If they were ever to achieve the size of a dog our worst nightmare would surely have come to pass.

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