Along come the spiders
Updated 8:42 am, Friday, October 26, 2012
They're creepy and their spooky ... or are they? What you may not know about these rather fascinating eight-legged wonders. It's my happy Halloween notebook to you, spiders.
They belong to the class Arachnida, hence their fancy name arachnids. All spiders have eight legs and two body segments. The upper segment is called the "cephalothorax," which is where their eyes (most spiders have eight eyes, a main pair and then three smaller pairs), brain, stomach and jaw are located.
Their legs attach to this segment; two pairs face forward, two pairs face behind. All are covered with tiny hairs that are used to sense vibrations and smells from the environment around it — they have no noses. At the end of each leg are two or more tiny claws and six joints on each of their legs, so they can claim 48 knees!
Spiders don't 'chew' their food, but instead ingest it in a very eerie way. The jaws, called "chelicerae," house a pair of hollow fangs. Behind each fang are venom-producing glands. The captured prey is injected with the venom and, depending on the species of spider, the venom will either poison or paralyze the victim.
Next to each fang are appendages that act like little arms, called "pedipalps" or "palps" for short, that help hold onto the prey as the spider ingests it. Once incapacitated and grasped, the spider begins to regurgitate digestive juices from its stomach through its fangs, piercing its prey. The acidic juices dissolve the unfortunate visitor's innards into a liquid blob that can then be sucked out. If you have ever seen an insect in a spider web that appears dead, chances are it's an empty corpse, drained clean. Some spiders cover their prey in the acidic stomach juice so it softens, then use their jaws to crush it into a pulp-like meal and slurp it up.
The lower segment is dubbed the abdomen, here can be found the heart, lungs, liver and silk-producing glands. These glands are connected to spigots or openings on their abdomen where the liquid silk threads are released. Each "thread" is a number of teeny thin threads intertwined that harden once they meet the air.
Protecting and keeping the shape of both segments, since a spider has no internal bones, is a hard outer covering called an "exoskeleton." Some spiders can molt or shed their exoskeleton up to 12 times before they reach maturity. They do this by crawling out of the old and stretching the underlying new covering by inflating it with air so it hardens a size or two larger. They then grow into and eventually out of that one and the process starts all over again.
All spiders produce silk, but not all spiders are web spinners. The silk threads are also used for wrapping their prey like a mummy, lining the walls of a burrow, protecting their eggs and draglines (think Spiderman and how he traveled). These draglines can connect them to a new location by catching a breeze and floating the spider in the air and can be a lifesaver.
Those that spin webs do them as an artform, and each species makes its own style. Most webs are crafted to catch prey, but there are some spiders that prefer to hunt. The art of spinning a web is innate; it is not taught.
There are webs that resemble a funnel that a prey enters and can't escape. A common style is the one that looks like a bicycle wheel with spokes. Some webs are reconstructed daily; others are home for the life of the spider.
When males become sexually mature, their "palps" transform into syringe-like appendages. He spins a small silkened area where he deposits a bit of sperm, which he then sucks up into these syringes. Once the female is attracted he inseminates her using one of his "palp"syringes — that is, of course, if she doesn't kill him and eat him first, which is what some species do.
Most of our local spiders live about a year. In fall, the females lay their eggs, which hatch come spring, mature and then die as adults the following fall. Some overwinter in cracks and crevices, under rocks and bark by transforming their blood into an "anti-freeze"-type fluid.
Happy Halloween to all and a very Happy Sweet 16th Birthday to my daughter, Leah!