Critters with Eight Legs

It could happen to you.

You're strolling down a garden path or sidewalk when suddenly you walk into a Spider Web.  As you desperately try to get the thin sticky yuck off off you, consider who put it there.

OK.  There probably aren't Giant Spiders building webs with human prey in mind.  Still, I've gotten spider silk in my hair on my arms enough times to wonder about it.  So I did a little research on Spiders.

The biggest spider eats birds, so human beings becoming Spider Chow is not very likely.  (We'll leave that scenario to the movies).


As most people know, Spiders are not insects.  Insects have six legs, Spiders have eight.  Spiders are of the class Arachnida which includes other eight legged creatures with exoskeletons, for instance:  mites, ticks and scorpions.  Spiders are categorized still further based on their various structures and behaviors -into some 38,000 species.



Some Spider Facts:

-found everywhere, except possibly, Antarctica and the Ocean
-life span 1-2 years (an exception: female Tarantula's life span is 10-20 years)
-most spiders have 8 eyes, but some have as few as 2
-legs are used for locomotion, taste, sensing objects for navigation, and sensing vibration
-range in size from 2 millimeters to the size of a small pizza
-typical litter size: 100
-venom is mainly used to subdue prey, only a few species have venom that can harm mammals


The Spider Body

The body of the Spider is made up of two main parts: the Cephalothorax (head and thorax) and the Opisthosoma (abdomen).  The Cephalthorax contains the eyes, mouth, fangs, brain, poison glands, stomach and legs.  The Opisthosoma houses the heart, digestive tract, reproductive organs, lungs and silk glands.  The two sections are attached by a small waist, or Pedicel.

There are many variations in Spider appearance but they all have this basic framework.  Some Spiders are hairy, some are not.  Some are bland in color, some quite garish.  Some species are able to change color for camouflage allowing them to blend into such backgrounds as leaves, tree bark and bird droppings.



Baby Spiders and the Creation of Them

Male and female Spiders live apart. When it's mating time, the male finds the female usually via Phermones.  Sometimes the male is much smaller than the female and she barely notices him when he inserts his seed.  Male Spiders don't have a penis.  The male transfers sperm from his testes to his palp (finger like appendage near the mouth).  Then, when he finds a willing (or indifferent) female, he inserts the sperm.  Sometimes the male is at risk of being killed either before, during, or after the event.

Many Spider mothers build a silk sack around their eggs and guard the sack from predators.  When the babies hatch they eat their egg, then cut their way out of the silk sack.  Some Spider moms allow the babies to ride on her back for a week or so.  At that point, the babies molt and go out alone.  The molt only happens to youngsters.  Because the exoskeleton is stiff, it must be shed to allow for growth.  Some Spider moms will regurgitate food for the babies, some moms will offer up their bodies for her children's final feeding before they must fend for themselves.



Webbage

Not all Spiders spin webs.  The web silk is formed inside the Spider's body and projected out through a spinnerette located in the abdomen.  Silk comes in different strengths (sort of like fishing line does).

When we think of webs, we usually envision the orb/symmetrical design (like Charlotte's).  Spiders employ other ways of webbage, such as:  blanket, clump, scaffold, hammock, funnel.  Other Spiders don't use a web to capture prey, they hunt using stealth, ambush, diving underwater, bungee jump using a silk thread, or steal food from another Spider's web.  To avoid getting stuck in webs, Spiders walk on their tip toes or stay on the non sticky strands (remember there are different "grades" of silk, some are non stick).

That webbage you walk into on a garden path, where it appears that places to begin and end a web are several feet apart?  Most likely, it is a Spider that uses a single line or two, like a tight rope.  The Spider is able to catch insects using a narrower trap.  The theory is, the Insect (or you) cannot detect the single line as well as a cluster of lines, making it more difficult to avoid.

Spiders sometimes hang out just after a molt, for protection.  Their bodies are vulnerably soft for a while, before the exoskeleton hardens. 

They also hang around in search of victims.  (boowaaraahh!)



















sources:

The Natural History of Spiders  by Ken and Rod Preston-Mafham

The World of the Spiders  by Adrienne Mason