Sunday, 10 September 2023

Are daddy-long-legs really the most venomous spider? Here's the truth behind the myths.

Extract from ABC News

Posted 
Close up of spider with eggs
Female 'daddies' make great mothers, carrying their eggs in a sack everywhere they go.()

Daddy-long-leg spiders are in homes throughout the world – but there's so much about them that is misunderstood.

For a start, they're not all actual daddies, says Samantha Nixon, a research scientist from the University of California, San Francisco (UCSF). 

Dr Nixon is originally from Queensland and credits the daddy-long-legs for helping her switch from an arachnophobe to a spider-loving venom scientist.

She's going to help us clear up a few myths and misnomers about the daddy-long-legs.

Dr Samantha Nixon in a lab
Samantha Nixon works with spiders at the University of Queensland.(Institute for Molecular Bioscience, University of Queensland )

Are they really the most venomous spider in the world?

You might have heard the claim that daddy-long-legs are really dangerous, but they just don't have big enough fangs to bite us.

There are a few versions of this story, but according to the experts it just isn't true.

Studies have found, for example, venom from daddy-long-legs is much less toxic than that from the black widow spider, Dr Nixon says.

"They found that it's very different to the venoms of funnel webs or black widows or redback spiders that we consider medically dangerous, and generally it was just much weaker than those."

The venom does have enzymes that contribute to breaking down the spider's prey, but it is generally not dangerous to people.

According to Lizzy Lowe, from Invertebrates Australia, the idea that daddy-long-legs are venomous is "one of these myths that just refuses to die".

"I think Australians love the idea that they live with a super-venomous spider in their houses and that's why it's kind of perpetuated for so long," Dr Lowe says.

Can they actually bite humans?

The idea that daddy-long-legs have fangs that are too small to bite humans is a myth, Dr Nixon says.

"The daddy-long-legs have very, very small fangs, which means that it is a little bit harder for them to pierce through our skin."

Daddy-long-legs spider.
Daddy-long-legs like this are a common sight in Australian homes. (Supplied: Katie Kanowski)

But another type of spider that has these kinds of small fangs is the brown recluse spider (found in North America); it is clearly capable of biting people and is considered dangerous.

So, it's not that daddy-long-legs can't bite us, they probably choose not to, Dr Nixon says.

"If you don't stress the spiders out [they] will choose not to bite you. They prefer to run away if they can."

The ability of daddy-long-legs to bite a human was  documented on television back in 2004 when the host of MythBusters, Adam Savage, put his arm in a tank of daddy-long-legs and got a small bite.

"It was very mild, a little bit of pain and itching that faded very, very quickly," Dr Nixon says.

Do they only eat insects? 

Daddy-long-legs may look cute, but they're actually assassins.

Apart from eating insects they also eat some of the most dangerous spiders we have in our houses such as redbacks, as well as more maligned species like white-tailed spiders.

"They are actually quite handy little things to have around the house," Dr Lowe says.

"We've got a lot to thank them for."

Daddy long legs trapping an ear wig
The daddy-long-legs can easily take on an earwig and other household insects and spiders. (Supplied: Paul Irvine)

Are they really  spiders?

The Australian ones are, but the US ones aren't.

Daddy-long-legs spiders in Australia are a part of the Pholcidae group, commonly called cellar spiders.

"There's more than 1800 species of cellar spiders found around the world," Dr Nixon says.

In the US, though, the name daddy-long-legs is given to a creature called a harvestman, which is not a spider.

Harvestman spider sits on a leaf, close up shot
The US version of the daddy-long-legs, a male harvestman (Hadrobunus grandis).(Wikimedia Commons: Bruce Marlin)

"Harvestmen are a group of arachnids that are not spiders yet they look similar."

Dr Nixon says they are a group of arachnids called opilionids that don't have venom or fangs.

"They look like ovals with very, very long legs. The head and the body look fused together.

Are daddy-long-legs good mummies? 

Despite their name, these spiders are not all "daddies". In fact, female daddy-long-legs are very good mummies.

They are extremely careful with their eggs and rather than leave them in the web, take them everywhere with them.

"They actually wrap them up in the beautiful little sack which they'll carry around with them until the little ones are ready to hatch," Dr Lowe says.

"Once they hatch, they're on their own but up until then the mother will look after these eggs and carry them around to make sure that nobody else gets to them."

Baby spiders hatching from sac
These baby daddy-long-leg spiders are hatching after being carried by their mother. (Supplied: Paul Irvine)

Let's respect the daddy-long-legs!

Daddy-long-legs are a misunderstood spider, but Dr Lowe says they should be celebrated.

She says the species you probably have in your house right now is most likely one that became adapted to post-European civilisation.

"We come in, we change the whole environment and they're like 'Yep this is my home now'. They take on board whatever changes we've made and they live alongside us."

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