Your Daily Facts about Spiders
Spiders came up now because I am watching a weird show on the SYFY channel called Arachnophobia. About a killer spider from Venezuela that breeds more killer spiders. A bit of a campy movie. And no, this aint gonna happen in real life!
Amongst the vast numbers of invertebrate animals in the Phylum Arthopoda, more than a million different kinds have bodies with three main parts–head, thorax, and abdomen. The head has eyes, antennae and mouthparts. The thorax has three pairs of legs. The entire body is protected by a tough outer covering called an exoskeleton. Animals that share these characteristics are called insects. The group to which they belong is called the Insecta.
Another, smaller, group of invertebrate animals has only two main body parts. The body consists of a combined head and thorax called the cephalothorax, and the abdomen. The cephalothorax has the eyes, mouthparts (no antennae) and four pairs of legs. Animals that share these characteristics include ticks, mites, scorpions and spiders. The group is called the Arachnida.
Within the Arachnida, spiders are classified into a special group called the Araneae that separates the spiders from the ticks, mites, and scorpions. A distinguishing characteristic of spiders (Araneae) is that they have a very slender waist or pedicel separating the cephalothorax from the abdomen. The cephalothorax is covered by a tough carapace. Spiders are believed to have existed for more than 300 million years.
A spider’s body consists of:
a) a cephalothorax with eyes, mouthparts – a pair of jaws and a pair of pedipalps, and four pairs of jointed legs and
b) an abdomen connected to the cephalothorax by a narrow pedicel. The entire body is encased by a tough protective exoskeleton and much of the body has sensory hairs growing from the skin.
Spiders have silk spinning glands called spinnerets, at the tip of their abdomen.
Not all spiders spin webs.
There are more than 30,000 species of spiders.
While most spiders live for one year, a few may have more than one generation each year. Some spiders can live 3 to 4 years, and certain tarantulas are known to live for 25 years or longer.
Spiders are oviparous, which means their babies come from eggs.
Most spiders have either six or eight eyes.
Most spiders have fangs, through which venom is ejected.
Spider bites can be quite painful, and a select few can be fatal.
Below the eyes on head end of a spider’s cephalothorax are two small jaws (chelicerae) that end in fangs. Venom (poison) is produced in glands behind the jaws and empties along ducts in the fangs to paralyze or kill prey. Relatively few spiders bite people because they are not able to pierce the skin with their fangs. The majority of those spiders that can bite people have venom that is harmless to people. Two notable exceptions in the United States are the Brown Recluse, and the Black Widow.
When dealing with the effect of spider venom on humans there are two types. Some spider venom is neurotoxic; that is, it affects the human nervous system beyond the site of the bite. The black widow venom is neurotoxic. A principal component of this venom is a-latrotoxin. A black widow bite causes rigidity , cramp, and paralysis of the sympathetic systems. Occasionally it causes death. Other spider venom is necrotic and causes damage to the tissues surrounding the site of the bite. The recluse spiders have necrotic venom. The damage usually results in skin blisters, ulcers and blackening of the local tissues.
While there are only a few spiders in the United States that are really dangerous to humans, there are significant numbers around the world. The black widow and recluse spiders have very toxic venom that can be life threatening to humans. Some wolf spiders in South America, and some running spiders (family Chiracanthium) worldwide have venom that causes painful symptoms in humans. Pigeon spiders of West Africa give very painful bites. In Australia there are between 50 and 100 venomous species at least two of which can be life threatening to humans, the red-back and the Sydney funnel-spider.
Fear of spiders is called Arachnophobia. It is one of the most common fears among humans.
Spiders eat many types of harmful insects, helping to keep your garden free of pests.
Most spiders are very nearsighted. To make up for this, they use the hair on their body to feel their way around and to sense when other animals are near.
Webs get dirty and torn, so lots of spiders make a new one every day. They don’t waste the old one, though–they roll it up into a ball and eat it!
Young spiders resemble adults. Only their size and coloration differ.
Male spiders are usually smaller than female spiders.