How accurate is the spider science in Doctor Who: Arachnids in the UK?

Is spider silk really as strong as steel? Can spiders grow for ever? And why would one be stopped by vinegar? We ask an expert to check the science fiction against the science facts


Doctor Who series 11 episode Arachnids in the UK sees the Doctor (Jodie Whittaker) and her friends take on an infestation of massive eight-legged mutant spiders in Sheffield.


We know. Freaky.

In the course of the episode, writer Chris Chibnall also introduced us to all sorts of fascinating spider facts, with the help of zoologist Dr Niall Doran.

But just how accurate were the facts that made the final cut? Would it actually be possible for spiders to mutate into giant, aggressive creatures? And even if not, did the science in the episode stack up?

To find out, we asked naturalist and British Arachnological Society spokesperson Lawrence Bee.

We’ll be going through some of the facts suggested in Doctor Who step by step below, before discussing the wilder science-fiction elements, but be warned – this piece contains spoilers…

If you don’t want to know what happens, scuttle away now.

Spiders’ feet are their noses

The Doctor makes this claim fairly early on in the episode, and according to Bee it’s fairly close to the truth.

“To some extent, yes, that’s true,” he says.

“They have hairs on their legs which act as sense organs. It’s not a sense we possess, so it can be difficult for us to understand.

“They have what’s called a chemotactile sense, and they do pick up information through these fine hairs on their legs. So yes, that’s fine.”

Spiders hate the smell of garlic

Doctor Who Series 11

While this is a fairly common remedy against spider infestation (explaining why the Doctor whips out some garlic to contain an oversized house spider), Bee says there’s not much scientific research to back it up.

“It’s not scientifically proven, I don’t think,” he says.

“There’s a lot of old wives tales about spiders. It’s said that they hate the smell of chestnuts and again, people will swear that they put horse chestnuts on their windowsills and it keeps the spiders away.

“But there’s no scientific evidence to prove that whatsoever, and I think the same applies to garlic.”

Vinegar poured in a line could stop a spider


The Doctor also stops the oversized spider in its tracks by creating a line of vinegar on the floor and walls which the spider is unwilling to cross.

But while once again, vinegar has been suggested as a method of deterring spiders (usually sprayed at them or on surfaces), Bee is dubious whether the use of it in the episode would actually stop a spider (especially one that big).

“They would obviously prefer to be on a dry surface compared to a damp surface just for ease of movement, I suppose,” he says.

“They wouldn’t survive if they’re immersed in it, but I’m not sure there’s a question of spiders approaching it and going, ‘Ooh no, I don’t like that.’

“They will avoid things which are probably going to harm them. You might, at a stretch, suggest that ascetic acid in vinegar would be something they’d avoid, but I don’t think a line of droplets is going to have much effect.

“I don’t have any scientific evidence one way or the other, but it’s not something I’m aware of,” he concludes.

Some people have reported success deterring spiders by spraying windowsills and surfaces with vinegar solution, so it’s not a completely strange thing for the Doctor to attempt.

There are said to be 21 quadrillion spiders on Earth


This statistic, suggested by arachnologist Jade (above) in the episode, might seem incredible – but Bee says the number is certainly possible.

“21 quadrillion… well it’s certainly quite a large number!” he laughs.

“If you take a hectare of grassland in the UK, you might expect to find anything between two and two and a half million individual spiders within that area. We’re talking about extremely tiny mini-spiders, but one of those is a spider. So that’s the kind of figure we’re talking about.

“And I think there is some research done last year in the States that worked out that the amount of insects that spiders consumed annually throughout the planet was greater than the weight of the whole human population.

“It just shows how useful they are as pest controllers. When you look at it planet-wide, things get a bit crazy.”

Ordinary spider silk is as strong as steel and as tough as Kevlar

Shobna Gulati with Mandip Gill in Doctor Who: Arachnids in the UK (BBC, HF)
Shobna Gulati with Mandip Gill in Doctor Who: Arachnids in the UK (BBC)

Doctor Who’s description of spider silk’s durability is fairly accurate, apparently, and many scientists really are trying to unlock the material’s full potential.

“Size for size, it is extremely strong,” Bee tells us.

“We say it’s as strong as a ship’s steel cables, size for size. So if you had a strand of spider silk as thick as a steel cable on a ship, yes, it would be as strong if not stronger.”

Dragline spider silk woven thick as a pencil could stop a plane mid-flight

Following on from this, is the Doctor’s next fun fact also true?

“I wouldn’t like to be quoted as saying yes that’s true!” Bee said. “It could possibly, but it’s a difficult one.

“I do know they’ve been experimenting in the States with trying to reproduce spider silk artificially to weave as a material that they would use in bulletproof vests. Because the strength of it is supposed to prevent a bullet breaking through it.

“The research is still going on. I don’t think they’ve actually achieved anything with it yet. But yes, spider silk is very strong indeed.”

Spiders keep growing for as long as they live


This fact is a crucial plot point in the episode, as Jade’s team’s attempts to create a spider with a longer lifespan end up leading to the creation of a massive mutant giant spider.

However, according to Bee, the facts aren’t quite that simple…

“No, they don’t keep growing,” Bee says. “They will grow until they reach the adult stage, at which stage they stop growing.

“Obviously as adults they’re concerned with finding a mate and producing the next generation. So they’re still alive there, but they’re not actually growing at that stage.”

However, the episode’s depiction of spiders shedding their skin as they grow does seem fairly spot on, so it could be that in this science-fiction scenario – where the genetically altered spiders were also exposed to toxic chemicals – the growing stage lasted a lot longer, even if it did reach an end point.

“From the time that they hatch from eggs, they go through a series of moults, and immediately after the moult the tissue will harden up, but there is a short period of time where they can grow in size,” Bee says.

“If it’s a small adult it might go through three or four moults. If it’s a larger beast it might go through six to eight moults before it reaches the adult stage.

“So there’s a variety of processes according to what spider you’re talking about,” he adds.

“But the statement ‘they continue to grow’ is not true in that they stop growing when they reach the adult stage.”

Spiders find their food by vibration

Chris Noth as Robertson in Doctor Who (BBC)
Chris Noth as Robertson in Doctor Who (BBC)

At the end of the episode, Ryan (Tosin Cole) has the idea of playing grime music to trick the mass of spiders into entering a panic room. In real life, certain spiders do ideed find their food by vibrations.

However, they normally only do this through the silk of their webs, meaning Doctor Who took a slight science fiction leap for the story’s conclusion (though technically, at one point it’s suggested the spiders feel the whole building as their web, which could explain the discrepancy).

“Spiders in an orb web for instance will keep their legs on the strands of silk and receive messages of struggling insects via the silk in the web,” Bee says.

“So in that sort of thing, vibration, yes. With some spiders, one way you can tempt them out of their webs is to hold a vibrating electric toothbrush against the silk and they immediately rush out and grab hold of it, thinking it’s some potential prey.”

However, not all spiders hunt their prey in this way.

“Vibration via silk is usually going to work for those spiders which spin a web,” Bee explains.

“Other ones, no. Jumping spiders and wolf spiders, for instance, use their eyesight. And there are others which use a combination of eyesight and vibrations. And of course there’s the sense we mentioned earlier that we don’t possess, this chemotactile thing, which obviously enables them to sense their surroundings and see things around them. And food may be part of that.”

Giant mutated spiders would have altered behaviour


To be fair to Doctor Who, most scientific leaps of faith in the episode can be explained by the fact that these are no longer normal spiders, having been born from a mutant, genetically altered creature that doesn’t actually exist.

According to Bee, it does make sense that these spiders would behave differently and become more aggressive, even towards humans.

“It’s not a completely way off idea,” he says. “Spiders aren’t normally aggressive, despite what you might read in the papers.

“If they are threatened, like any creatures they’ll try and defend themselves. And as they are able to break human skin and their venom is quite potent, then they might cause a reaction if one is bitten by them, as does occasionally happen.

“When people are bitten by spiders, if you’re sensitive you’ll react in the same way you would to a bee or a wasp sting, and that’s about as far as it goes,” he goes on.

“People talk about ‘deadly spiders,’ but there’s been no reports of anybody being killed by a spider in this country. People do die of being stung by bees or wasps. We have to put it in perspective.

“Obviously from what you’re saying and in the story, as they grow larger they may behave oddly – but I mean we’re really getting into science fiction. I can’t really comment on the likelihood of this sort of thing being true.”

Which might make this next question a little tricky too…

Would a giant spider really suffocate?


At the end of Arachnids in the UK, our heroes expect to face off against the biggest spider of all – but they find it struggling to breathe thanks to its huge size. It’s no real threat to anyone.

Is that something that would really happen?

“I think the ability to survive restricts the size to which the spider can grow, as it would do with anything I suppose,” Bee suggests.

“I mean from a science fiction point of view, I suppose that could be based on some real science, in that the size of any living organism is controlled by these sorts of factors.

“We talk about flying insects and how big they could be. Well, it survives on flying around looking for food. If it grows too big, it’s not going to be able to fly. So that sort of factor is going to be quite a control to the size of the animal.

“In a very vague way, that is based on some science,” he concludes.

Is Arachnids in the UK scientifically accurate?


Overall, then, how well does Arachnids in the UK present scientific facts about spiders?

“They’re not going completely mad with it,” Bee says. “The idea of the spiders changing dramatically having been exposed to some sort of agent – once you get beyond that, it’s not science anymore, because you’re changing all the ground rules.

“But what you’ve been saying is not completely off the planet by any means.

“As with all science fiction, I suppose, you have to suspend your disbelief for various principles and allow the thing to develop,” he says.

In other words, you could do a lot worse than picking up a few spider-facts from this week’s episode – just so long as you do a bit of research afterwards to see how well they apply to our real eight-legged friends.

Doctor Who continues on BBC1 on Sundays


This article was originally published on 28 October 2018