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Spiders

Orb spider making silk Spiders are a type of arachnid. They have eight legs and two grasping "limbs", called pedipalps. Spiders rely more on sound than sight. Most species have bristles on their legs that are sensitive to vibrations in the air or through the ground. Spiders feed by piercing their prey with their sharp fangs, paralysing or killing them them with their venom. Their saliva turns the body tissues of the prey into liquid that can then be sucked up. A few species are so venomous that they can kill humans. All spiders make silk, but not all spiders build webs. Spiders that do not spin webs, such as the tarantulas, chase down or ambush their prey instead.



Cross-section through a spider
Spiderweb

Spiderwebs

Many spiders catch their prey by spinning webs out of spider silk. Webs can be of a great variety of shapes, including delicate spirals, irregular cobwebs or thick funnels. Any insect that flies into a web is caught in the strands, which are often sticky. As the insect struggles to free itself, the spider, sitting at the edge of the web, feels the vibrations and comes to claim its prey. It avoids becoming caught in the threads itself by walking on the claw-like tips of its feet.
Making a spiderweb: 1. The spider joins two branches with a line of silk. 2. A vertical line anchors the web at the bottom. 3....Read More >>Making a spiderweb: 1. The spider joins two branches with a line of silk. 2. A vertical line anchors the web at the bottom. 3. Radiating lines are linked together at the central hub. 4. The spider lays down the sticky spiral strands. 5. The spider waits for its first victim in the dry centre of the web.Some spiders, known as tangleweb spiders, weave the irregular, three-dimensional webs commonly known as cobwebs. They are less careful weavers, and may take several days to complete a web.

There are 350,000 known species of spider.

WHY IS IT COLD
AT THE TOP OF MOUNTAINS?


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