Which Spiders in Spain Actually Bite? 6 Questions Answered
More than a thousand spider species live in Spain, yet almost none of them pose a medical problem. We answer six common questions, from the myth that we swallow spiders in our sleep to which ones can actually bite you.
Do we swallow eight spiders a year while we sleep?
No. The figure has been circulating for years, but no one has ever found the study that supposedly measured it.
There is also a physical reason. Spiders sense their surroundings through vibrations, thanks to hairs and sensory organs on their legs. A sleeping person breathes, has a pulse and sometimes snores. According to arachnologists, for a spider, approaching a mouth is like walking right alongside a truck with its engine running is for us: everything signals danger.
Are spiders insects?
No. They are arachnids, like scorpions, ticks and mites. Their bodies are divided into two parts, not three. They also have no antennae or wings. They resemble insects in some ways, but they are separate groups.
Why don't spiders stick to their own webs?
It is often said that their legs are coated in oil. That is only part of the explanation. In an orb web, not all the threads are sticky. The radial threads, which run out from the centre, are dry. Only the spiral carries adhesive droplets. The spider moves mainly along the radial threads and grips the silk with a hooked central claw.
In 2012, a Smithsonian Institution study of the golden orb-weaver found two further defences: branched hairs on the legs and a non-stick chemical coating. When their legs were washed with a solvent, the spiders stuck more. The hairs reduce the contact area, much like touching adhesive tape with a brush instead of your palm.
Are all spiders venomous?
Almost all of them. Of the more than fifty thousand described species, the major exception is the Uloboridae family, which lost its venom glands.
To hunt, these spiders wrap their prey in silk, turn after turn, until it is immobilised. They then soak it in digestive juices.
Why do more spiders show up indoors in autumn?
They don't usually come in to escape the cold. Many were already living inside.
The large, dark spiders that dash across the hallway in September and October are usually male house spiders of the genus Eratigena. They have just reached adulthood, leave their hiding places and roam the house looking for a female.
Which spiders in Spain can actually bite you?
More than a thousand spider species live in Spain, and almost none of them are a medical problem. Two deserve attention.
The Mediterranean black widow. The female is black, measures one centimetre and has up to thirteen red spots. It lives under stones and in cereal fields. Its venom acts on the nerves, causing intense, spreading pain, cramps, sweating and a rigid abdomen. In a healthy adult it very rarely kills, and it is treated in hospital.
The violin spider. It is brown and has a violin-shaped mark on the front part of its body. It hides behind furniture and pictures. Its bite can open an ulcer that takes weeks to heal, although it almost always amounts to no more than a red patch.
Below these come the yellow sac spider, whose bite hurts like a wasp sting, and the false black widow, whose bites are mild.
One important point: when doctors review suspected spider bites, many turn out to be skin infections caused by bacteria such as staphylococcus. If nobody saw the spider, it most likely wasn't a spider.
Frequently asked questions
What is the most dangerous spider in Spain?
The Mediterranean black widow. Its venom acts on the nerves, although in a healthy adult it very rarely kills, and it is treated in hospital.
How can you recognise a violin spider?
It is brown and has a violin-shaped mark on the front part of its body. It usually hides behind furniture and pictures.
Are there spiders without venom?
Yes. The Uloboridae family lost its venom glands and hunts by wrapping its prey in silk.
Can a suspected spider bite be something else?
Yes. Many turn out to be skin infections caused by bacteria such as staphylococcus, especially if nobody saw the spider.
Informative article written with the help of AI tools from the verified script of the video. The video is in Spanish.