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Wildlife Wonders

Today is Spider Day!

Spiders are so amazing and for any of you who may suffer from arachnophobia (an intense and “unreasonable” fear of spiders) I am sure your will have a new appreciation after you get to know more about them!

Spiders are arachnids, closely related to scorpions, mites and ticks.  Spiders are the largest group of arachnids and although I must say after looking at various references (books and websites) the number jumped from 35,000 to over 45,000 spiders identified worldwide.  Still scientists believe that there are probably twice as many spiders.  So there are a lot more that have not been identified.  In North America alone there are about 3,000 species!  Spiders have existed for well over 300 million years and they live in almost every kind of “habitat”.

Unlike insects, that have 3 body segments (head, thorax and abdomen), spiders have 2 body segments the cephalothorax (a combined head and thorax) and the abdomen. The cephalothorax is where the 8 legs are connected. The legs end in claws and are covered with tiny hairs to help detect vibrations. The cephalothorax also contains the brain, mouth and fangs to inject venom to paralyze their prey and simple eyes, they usually have 8 eyes, some have six.  Most spiders do not have good eyesight and rely mainly on touch.  The exception, and there always seems to be one, is the jumping spider which hunts during the day and can see more colors than humans can. 

The abdomen has spinnerets at the end (2, 4 or 6) where silk is produced.  Many, but not all spiders use silk to make webs.  There are many other uses of silk.  Most create a “dragline” and secure it behind them for safety.  If they get knocked off something they use their “dragline” to climb back up.  Small spiders do what is called “ballooning” they travel long distances by catching the wind and sailing through the air using silk threads.  Silk is used to construct nests, line burrows and attach trap doors. They wrap their eggs with it and “mummify” or wrap their prey.  Spider silk is the strongest known natural fiber, it is half the strength of steel. 

Some spiders are classified by the type of webs they weave.  Orb webs look like a wagon wheel. Tangled webs are cobwebs often seen in basements, sheet webs are usually low to the ground between blades of grass or shrubs and trees, triangle webs are found in shorts grasses or shrubs or between building. See Growing Up WILD, Spider Web Wonders.    

Spiderlings are newly hatched spiders that look like tiny adults.  Depending on the species egg sacs can produce 2,500 eggs, most are eaten by predators before they become adults. They go through 5-10 molts and at this time they can grow new legs if they lose them.  When they are adults they are no longer able to “regenerate”, or grow, new legs.  Most spiders live 1-2 years, some live only a few months, and others like the female tarantulas and trap door spiders can live up to 20 years!

All spiders are carnivorous and venomous.  Most feed on live insects some feed on small vertebrates The body of the victim is pierced with the fangs, venom is secreted to paralyze or kill the prey, digestive juices from the spider liquefy the insides of the insects and through the pumping action of the spiders stomach the juices of the insect are sucked out.  Some spiders simply seize their prey, hold it in their fangs and eat it.  In North America most spiders are not dangerous to humans, except for the black widow and brown recluse.  Most are harmless to people, but a few may bite to defend themselves.  A good rule around all spiders is look, but don’t touch!

The largest spider is found in South America.  It is called the goliath bird eating tarantula it has a leg span of 10″ and an abdomen of 3.5 inches.  The tiny Samoan moss spider is 0.1 inch long and a leg span of 0.11 inches.

Spiders have cool adaptations:

  • Jumping spiders can jump up to 40 times their length.
  • Crab spiders can change their color to match the color of the flower they are on.
  • Some spiders look like a twig, others look like bird droppings.
  • Trap door spiders live in underground tunnels with a trap door and when they feel vibration above they quickly open the trap door and drag their prey into the tunnel.  They can also hold the door shut with their fangs and claws, bracing their legs against the side of the burrow. 
  • Wolf spiders run after their prey.

Spiders are beneficial to humans because they keep insects under control.  Without spiders to eat insect pests it is believed our food supply would be at risk.  Medical researchers are studying spider venom to see if it can be used to treat disease in humans! 

Now don’t you agree they are amazing!!!

Resources:

https://animals.sandiegozoo.org/animals/spider

https://www.fishwildlife.org/application/files/2515/3488/5651/Spider_Web_Wonders.pdf

A House Spider’s Life by John Himmelman

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