Doug Scull s SCIENCE & NATURE THE ARACHNIDS The Arachnids are a large group of Arthropods, along with the Insects, Centipedes, Millipedes and Crustaceans. Like all Arthropods, Arachnids have a hard exoskeleton, no bones, and jointed legs. The Arachnid group includes the spiders, scorpions, mites and ticks. All Arachnids have 8 legs and live on land. THE SPIDERS Spiders are extraordinary creatures. They have two body parts, four pairs of legs, four pairs of eyes, venom, and spinnerets, which can make silk. Even spiders that do not make webs have spinnerets. Their silk is stronger than steel and very elastic. With it, they can make webs, draglines, parachutes, nests, and cocoons. A little-known fact is that spiders cannot eat solid food. They must eat liquids. However, they are predators, which means they catch and eat other animals. How do they do it? They must digest their prey outside of their bodies, with enzymes from their digestive systems.
There are many different types of spiders that live all over the Earth in practically every type of habitat. They come in colors including black, brown, white, gray, red, yellow, green, and orange. Most spiders live for about a year, but the tarantulas can live for 30 years. Spiders range in size from barely visible to the size of a dinner plate. Spiders are divided into 2 main groups- the True Spiders and the Tarantulas. True Spiders are the spiders most of us see in our yards. Some make silken webs, but not all do. True Spiders are smaller than the Tarantulas, the largest no bigger than 3-4 inches. True spiders have 2 fangs that move side-to-side. True Spiders live only one year. During this time they must grow rapidly, become mature and mate. The female spider then lays up to a thousand tiny spider eggs and wraps them in a silken egg sac. In some species, the female spider carries the egg sac on her spinnerets or in her jaws until the eggs hatch. In other species, the egg sac is hidden under a rock, attached to a plant stalk, or hung in a web. Tiny spiderlings (baby spiders) hatch from the eggs looking like tiny versions of their parents. Some spiderlings are on their own and receive no care from their mother. Other spiders climb onto their mother s back after hatching, where she feeds them. In some species the mother dies when the young are ready to go off on their own, and the spiderlings eat her carcass.
Tarantulas Tarantulas are large hairy spiders that live mostly in warm, tropical areas of the world. Some can grow as big as a dinner plate! There are around 700 kinds, or species, of Tarantulas. These Arachnids can live over 30 years. Tarantulas also have 2 fangs, but their fangs move differently than a True Spider. Tarantula s fangs are kept folded and swing forward when they bite. Many Tarantulas live in burrows underground. They will either use their fangs to dig them or else take someone else s burrow-home. Even though they do not spin webs, Tarantulas use their silk to make doors or soft walls for their burrow or, in the case of tree-living tarantulas, tunnel-shaped homes in trees. Tarantulas are nighttime hunters who will pounce on their prey. They eat insects, beetles and grasshoppers. The Goliath Bird-eating Tarantula species will eat larger prey, such as, lizards, snakes, frogs, bats and small birds. All Tarantulas have an interesting way of defending themselves. They have hairs on their abdomen (stomachs) that have sharp little barbs, or pokey things, on them. When threatened, the spider will rub these hairs with their legs and shoot them at their predator. That would hurt! Predators that the tarantula would be afraid of are weasels, hawks, owls, skunks and snakes. Their worst enemy is the Spider-Wasp. The female wasp will paralyze the spider by stinging it. She then digs a hole and puts the spider and her egg into it. When the egg hatches, the baby wasp will eat away at the paralyzed spider. The spider could stay buried alive for many days before the larvae hatch. One other predator that the Tarantula must fear is people. In some countries they are eaten. They are said to have a nutty taste kind of like peanut butter! (Ewwww!)
THE SCORPIONS Scorpions are arachnids (and not insects); they are related to spiders, mites and ticks. There are over 1,500 species of scorpions worldwide. They live on every continent except Antarctica. These venomous Arachnids live in almost every type of habitat, including deserts, rain forests, prairies, grasslands, forests, mountains, ponds and seashores. Most scorpions are nocturnal (waking at night), resting under rocks, in crevices, or in burrows during the day. After mating, a female may stay pregnant for over one year. Scorpions give birth to large litters of live young, who quickly climb onto the mother's back after birth; the mother cares for the young until they are able to hunt in a week or two. Some scorpions live as long as 25 years. Scorpions are carnivores (meat-eaters) that paralyze their prey with a stinger located at the tip of the tail. They eat insects and other small animals. Some scorpions can go for a year without food.
The sting of most scorpions is only irritating to people, but about 25 species of scorpions are capable of killing people. Thousands of people die each year from scorpion stings. Unlike other arachnids, scorpions have large, pincer-like claws that are used to grab and hold their prey. Most scorpions are from ½ inch to 9 inches long. They range in color from black to brown to tan to red. Tiny sensory hairs on the exoskeleton are used to detect touch, temperature changes, and sound vibrations.