Black Widow
All About Arachnids
No antennae, no wings – but they do have eight legs and often venom glands! Discover everything about arachnids!
What Are Arachnids?
Arachnids are not insects. They possess eight legs, unlike insects which have only six. This group includes spiders, scorpions, and mites. The head and thorax are fused together. Many arachnids catch their prey using webs, pincers, or venom. They lay eggs and are mostly solitary creatures. While arachnids may appear creepy, most are harmless and even beneficial as they consume insects.
Main Characteristics of Arachnids
1. Eight Legs
Arachnids have eight legs. These legs are more flexible and longer than those of insects. This provides an advantage: they can use their legs more precisely and in various ways. For instance, the front pair is used to explore their surroundings and capture prey.
2. No Wings, No Antennae
Most insects have antennae – many of them quite long. However, arachnids never have antennae. Instead, they rely on their legs or mouthparts. Arachnids also lack wings and are unable to fly.
3. Head and Thorax are Fused
Arachnids consist of two body segments: a thorax and an abdomen. The head is fused with the thorax. This adaptation makes them more resilient and stable for their lifestyle, aiding in hunting or grasping prey. Insects, on the other hand, have three body segments: head, thorax, and abdomen.
Arachnid Family Tree
Amazing Facts About Arachnids
- There are 110,000 species of arachnids.
- 51,000 are spiders, 50,000 are mites, 6,600 are harvestmen, and 3,500 are scorpions.
- Arachnids always have eight legs. Insects only have six legs.
- Arachnids don't have a good sense of sight, but they do have an excellent sense of touch.
- Spider silk is produced as a liquid in the spinnerets. It is excreted through spinnerets and spun into threads outside the body.
- Threads made from spider silk are incredibly strong yet flexible. They can even withstand four to five times more stress than threads made of steel.
- However: Not all spiders create a web from fine threads. Only 2,800 species do that.
- Almost all spiders possess venom glands. These are located in the front section and they deliver the venom through their sharp fangs or pincers into their prey.
- In the USA, the most dangerous spiders are the black widow and the brown recluse spider.
- In Germany, there are only four spiders that can penetrate human skin with their chelicerae: the yellow sac spider, the diving bell spider, the Nosferatu spider, and the garden spider. While their venom does cause pain, it is not lethal.
- Australia is home to the majority of venomous spiders.
- The most dangerous venomous spiders are the Brazilian wandering spider (South America) and the Sydney funnel-web spider (Australia).
- The largest spider is the Goliath bird-eater. It has a wingspan of 11-12 inches (28-30 cm) and can weigh up to 6.2 ounces (175 grams).
- The smallest spider is the web spider Patu digua, which belongs to the family Symphytognathidae. It measures only 0.015 inches (0.37 mm) in length.
- The fastest spider is the Moroccan flic-flac spider. It can run at speeds of up to 3.8 mph (6.12 km/h). In just one second, it can cover a distance that is 100 times its body length.
- Scorpions are also part of the arachnids. Scorpions have two pincers and a venomous stinger on their tail. Out of 3,500 species, around 25 are dangerous to humans.
- Ticks are also arachnids. They belong to the order of mites within the arachnids. They can transmit Lyme disease and tick-borne encephalitis.
Arachnid Family Tree
