Puppy-sized spider: How big can a bug get?

The enormous Goliath spider, spotted recently in Guyana, conjures images of horror movies. But don't worry: A spider probably can't get that big.

The spotting of a rare Goliath birdeater spider in the Amazon this week may have some wondering how far the boundaries of science can give as this arthropod skitters across into a realm more suited to comic books than science.

It makes some wonder if, perhaps not a Spiderman, but a spider the size of a man, could someday exist.

First described in 1804, the Goliath spider has a leg span of almost a foot and weighs up to a third of a pound, similar to the weight of a young puppy, according to a blog post written by Harvard entomologist and photographer Piotr Naskrecki, who spotted the spider underfoot during a nighttime walk through a rainforest in Guyana.

It is also likely the only spider in the world that makes noise as it walks, due to the “hardened tips and claws that produce a very distinct, clicking sound, not unlike that of a horse’s hooves hitting the ground,” writes Dr. Naskrecki.

The presence of a spider whose presence is announced by a clawing, thrumming skitter is the stuff of horror films.

This is the reverse of the The Incredible Shrinking Man (1957) where the hero is exposed to radioactive toxic waste and shrinks so small he ends up in a pitched battle with a “giant" spider.

However, according to the University of Chicago website called Fathom, we probably don’t have to be worried about anything too massive clacking its way out of the Amazon into, say, your shower, because science forbids it. 

Basically, if you double the size of an animal, you've got just four times the surface area trying to do the biological work – respiration, thermal regulation, not toppling over, etc. – needed to serve eight times the volume.

In other words, a spider the size of a house would probably collapse under its own weight. And because arthropods breathe through the surface of their exoskeletons, such an animal would have to figure out how to get oxygen to its cells far more efficiently than a normal spider can. Also, because animals shed heat through their surface, a house-sized spider would also likely overheat.

Of course, none of this stops filmmakers from tormenting their protagonists with monster spiders. One such filmmaker, Dustin Warburton, creator of the 2013 film Spiders, was ecstatic at the existence of a puppy-sized spider.

“I am so stoked,” Warburton said in a phone interview. “As soon as I get my next break I want to look into this because part of my film was a new species being discovered. Who knows what’s out there!”

In his zeal for gargantuan nightmarish eight-legged freak fodder Warburton speculated, “Maybe these spiders are like goldfish that grow into the environment that they’re in. Bigger bowl. Bigger fish.” 

Nobody knows what the exact upper limit for arthropods is, but the Goliath is probably near the upper range. A "bigger bowl" in this instance would probably mean a planet with lower gravity than Earth but with more oxygen in its atmosphere.

“All I can say is I’m excited,” said Warburton. “Imagine the things it could do!”

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Puppy-sized spider: How big can a bug get?
Read this article in
QR Code to Subscription page
Start your subscription today