Spiders evolved over 380 million years ago, and are a vital part of the world’s ecosystem. However, just because they’re old and important doesn’t mean some of them aren’t absolutely terrifying.

Here are to top 9 dangerous spiders in the world today:

Yellow Sac Spiders: The immediate bite of the spider is incredibly painful and can lead to redness and swelling. Luckily, unless someone has an allergy to the venom, there are rarely.

False Widow Spider: They are often cited as the most venomous spider in England and currently their population is expanding due to climate change. The symptoms of a bite are often quite different. However, the bitten area can swell up to the size of a tennis ball.

Brown Recluse Spiders: Are only found in central and southeastern United States and they are fairly small, about the size of a penny. Luckily, 90 percent of bites don’t require medical attention and usually don’t scar.

The Red Back Spider: A person usually experiences sweating (especially near the bite), nausea, muscle weakness and vomiting.

Brazilian Wandering Spider: After a bite, the person may experience a burning sensation in the area of the bite, along with goose bumps and sweats. About 30 minutes later, the person’s blood pressure may increase or decrease and their heartbeat may go faster or slow down. Nausea, abdominal cramping, blurred vision, hypothermia, vertigo, and excessive sweating are also symptoms of a bite from a Brazilian Wandering Spider.

Black Widow Spider: Most of the time people who are bitten by Black Widow Spiders don’t suffer any serious symptoms. However, according to National Geographic, their venom is 15 times stronger than a rattlesnake, so if they bite and inject a lot of venom, then the person could be in a lot of trouble.

Brown Widow Spider: The symptoms start with redness and swelling. This is followed by cramps and spasms that can last for several hours. Luckily, there are no recorded deaths from Brown Widow Spiders.

 

Funnel-Web Spider: After the bite, the person may start drooling because they have numbness around the mouth and excess saliva. They may also have a copious amount of tears. Soon they will have problems breathing and may lose consciousness.

The Six-eyed Sand Spider: Shortly after being bitten, hemorrhaging will start and the toxin spreads to the kidneys and liver, leading to death. Currently, there is no ant venom.