White-tailed spiders: Your questions answered

A recent blog about white-tailed spiders by spider expert Phil Sirvid prompted a flood of questions from our readers. Phil answers some of these and attempts to alleviate your fears.

CSIRO_ScienceImage_210_White_tailed_spider

White-tailed spider, 2004. CSIRO. Photo by David McClenaghan via Wikimedia Commons. CC BY-SA Gen 3.0

Dirty mouths

Question: I was under the impression that although their bite wasn’t particularly venomous, they are what is called a ‘dirty mouthed’ spider….much like the Australian Blue Tongued Lizzard, not having a venom that effects us, but that they can have nasty bacterium in their mouths (even necrotising)…is this NOT the case? Joanne.

Answer: While we can never say never, Joanne, there doesn’t seem to be anything to suggest that it’s normal for these spiders to do that. It’s also worth remembering we all have plenty of bacteria on the skin and some of these can cause problems if they enter wounds.

Necrotising venom

Question: Is there any truth to the notion that their venom is necrotising? (Not sure I’ve used the right term there) ie there is something in the venom that acts to break down cells and prevents wounds from healing? Holly.

Answer: The answer is no. Most people bitten by one of these spiders will find it annoying and painful but that’s about it. In theory it’s possible that some people might be more sensitive to white-tail venom. However, there is nothing to suggest necrosis is one of the more extreme responses. Even if some individuals might have unexpectedly strong reactions, the Australian study of 130 verified bites suggests these spiders are not going to cause serious problems for the population at large.

Bites and children

Question: Are there any special considerations for children, especially small ones? I tell people that white-tails aren’t dangerous and they say that it’s worse for kids because of small body size. From what you have just said (pain of bite issue aside) it sounds like body size has nothing to do with it, but it would be good to know if the study you mention included young children. Kate.

Answer: To answer the second part first, the study recorded 25 individuals as under 15 years old. In this case, there doesn’t seem to be any particular reason to worry more about children, although perhaps a young child might be a bit more sensitive to pain. However, bites from particularly venomous species such as black widows and redbacks can be worse for small children or the elderly.

Complications and confusions

Question: I thought the issue with white tail bites was the risk of serious complications? Steve.

Answer: There’s no reason to believe white-tail bites are particularly prone to complications, but later infection of bites or any other wounds can potentially be an issue.

Question: So, if it’s not white-tails causing those nasty wounds that are the subject of (frequent) media articles… what is it? I’m satisfied that white-tail “venom” isn’t the problem but clearly some people have a nasty reaction to something. Any ideas? Andy.

Answer: The picture is a bit cloudy. A large part of the problem is correct diagnosis. We know of cases where white-tail bites have been assumed by doctors and it’s turned out that there was another medical explanation for what happened. Over the years I’ve seen many media accounts where white-tails are blamed even though no spider was seen. As you can imagine, this only confuses things. Many of these accounts also mention treatment for infection. However, it’s usually not clear what happened to allow infection to enter the body and each case may be very different.

One thing’s for sure though, and that’s if you see a story where a white-tail is blamed even though the bite wasn’t felt, it was almost certainly something else.

Daddy long-legs and autumn numbers

Question: Should I keep all the Daddy long-legs in your house to help keep the white-tails at bay? Also, for the last few years we’ve noticed that every year in March is when we seem to get our yearly dose of white-tails inside the house. Is there anything about March or is that just a coincidence? We also get them come in, in pairs? Jaimee.

Answer: I wonder if the spiders you’re seeing in March are males. As we head towards autumn, males of many spider species reach maturity and wander about in search of females to start the next generation with. While I know first-hand that daddy longlegs spiders can catch and eat white-tails, I can’t guarantee what effect they’ll have on your local white-tail population!

Food thieves – an unusual observation

Question: The mason bees are doing there collecting as usual each summer. But we’ve noticed that by our back door we have a large colony of rather large white-tails that seem to be feeding off the spiders placed by the mason bees. They are getting through a window into our daughter’s room by the tens, and they’re never small. They look like a black and white wasp with legs! We don’t want to get bitten so will be bombing the back door soon unless you have other suggestions! Gus.

Answer: I’ve never heard of this before, but given those stolen spiders from the bees are very much alive but paralysed, I’m sure white-tails will find them to be quite tasty. Even better for the white-tail, unlike their normal prey, these spiders can’t even fight back. I’m quite astounded to hear you are seeing so many white-tails though. If they’re coming in via a window, have you considered some sort of mesh if you want to keep it open?

6 Responses

  1. Jennifer

    Great Q and A – thanks for that. I think my reaction to white tails is so violent (kill on sight) because of the way they are so overtly aggressive in their manner. Most spiders will run away if they see any human coming towards them, especially when they’re holding something to squash them with. I find that white tails, even tiny ones, tend to come towards you with their fighting form on. I know this must be inbuilt but it’s somewhat off putting!

    Reply
  2. Janet

    Thank you for all the interesting information about white tails.

    Reply
  3. MW

    Thanks Phil, this has been revelatory and I am starting to feel quite guilty of my fear of white tails. However, one thing I need to clarify (that I’ve been told by my husband who happily kills white tails because he believes himself to be protecting native spiders), do white tails kill native spiders?

    Reply
    • Phil Sirvid

      They most often eat the black or grey house spiders (Badmuna spp.) and like the white-tail, these are also Australian. These two house spider species (especially the grey house spider) are likely to be the commonest species seen on most house exteriors. However, I’ve seen them hunting native species too, so your husband is correct.

  4. Ginger Oates

    While Australia has been called a land running in venom, we in NZ have no poisonous spiders, no snakes, no scorpions. You could walk barefoot anywhere but for the broken glass. But because we arent familiar with nasty biting creatures we are frightened of them. There is a kind of national arachnophobia that lends credence to the misinformation about the white tailed spider.

    Reply
    • Phil Sirvid

      We actually have one native venomous spider, Ginger, and that’s the katipo. Most people will never see one though. Some parts of the country also have it’s Aussie cousin, the redback. It’s interesting that in the case of white tails, a lot of the unnecessary panic came from Australia. However, a lot of the research showing they’re more nuisance than dangerous has come from there too.

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