White-tails are blamed for lots of nasty symptoms, and have developed something of a bad reputation, but is it deserved? Bug expert Phil Sirvid sorts fact from fiction.
How painful is a white-tail bite?
A study of 130 verified white-tail bites from Australia found they were always very painful, although the authors did not find much in the way of other effects beyond local redness and swelling. So, treat white-tails with caution because the bite will hurt, but you shouldn’t expect much in the way of other consequences beyond minor local symptoms if you look after the bite wound.
None of this stops the white-tail being blamed for a variety of conditions even when there is no proof of a spider bite at all. Examples of such misdiagnoses have been reported in the medical literature. This is not to trivialise the very real symptoms people may be suffering, but nobody is helped by blaming the wrong culprit.
How venomous are white-tails?
White-tails are blamed for a lot of nasty symptoms, particularly in relation to the skin. However, studies have shown that there is nothing in white-tail venom that’s of particular concern for humans.
It’s theoretically possible that some people might be especially sensitive to white-tail venom, but there’s no evidence that this is true for the majority of the population at large.
Secondary infections (i.e. infection present in the environment entering a wound at a later time) are sometimes blamed on white-tails, even if no spider is seen. These can happen with any skin breakage, be it a bite, graze, or sting. In some cases this may be serious, but the risk of infection can be greatly reduced by keeping skin breakages clean.
White-tails may have a potential role here in that they are capable of breaking human skin with a bite, thus creating a potential entry point for infection to enter the body. However, there is no evidence to suggest these spiders directly transmit bacteria or other pathogens in the act of biting.
But even if their venom is not dangerous, white-tails deserve respect because of how mechanically strong their bite is.
Where do white-tails come from?
Some people think white-tails are a relatively recent arrival in New Zealand, but they’ve been recorded here since the 1870s.
They come from Australia and almost certainly arrived via the trans-Tasman transport of goods and people. They can go several months without feeding so a short sea voyage to New Zealand wouldn’t be difficult.
How many species of white-tail are in New Zealand?
We have two species currently recorded here. In the North Island we have Lampona murina while in the South Island we have L. cylindrata.
While it’s entirely possible that both species have been transported over Cook Strait, I’ve yet to actually see these spiders in the ‘wrong’ island. They’ve also reached more far-flung parts of New Zealand such as the Kermadecs and I’ve seen them in the Chathams.
Both species are very similar in appearance and you’d need a good microscope to separate them. They also have quite similar habits as specialist hunters of other spiders.
Where do they live?
By day they like living in cracks and crevices, something we humans provide in abundance with our homes.
They also like living under loose bark in tree species we’ve imported from Australia.
What do white-tails eat?
White-tails are helped to prosper by the presence of two other Australian species long-established in New Zealand, the black house spider, and the grey house spider (respectively Badumna insignis and B. longinqua). As their common names suggest, these like to live around homes and white-tails are quite happy to feed on them.
These are not the only spiders they prey on, but their abundance means these two species are a frequent food source.
When and how do they hunt?
The best time to see white-tails at work is after dark. The white-tail will very slowly and carefully enter a web. It starts plucking threads, trying to entice the web’s owner to come within attack range. Once it does, the white-tail strikes hard and fast. It needs to kill such dangerous prey as quickly as it can. Forcefully deployed fangs delivering venom ensure this happens. However, if the other spider attacks first, the white-tail will end up as prey rather than predator.
The myth about white-tails and daddy long-legs
One of the enduring myths about white-tails is that they are not especially dangerous to people unless they eat daddy long-legs spiders and co-opt their venom.
The story goes that the daddy long-legs is particularly toxic to humans, but its feeble fangs means it can’t bite people. This is all – to put it mildly – complete rubbish.
We know the daddy long-legs can bite and the venom is not dangerous. Even if it was, white-tails have no ability to transform their own venom by taking on the venom of another species. It would be a neat trick if they could.
It’s also worth noting the daddy long-legs is one of the white-tail’s more formidable opponents. That’s because the daddy long-legs is incredibly attuned to what’s happening in its web. No matter how careful it is, it’s virtually impossible for the white-tail to avoid being noticed. Once detected, the daddy long-legs will rain sticky silk down on it. In no time at all, the white-tail is wrapped in silk and is being hauled up by the daddy long-legs for lunch.