There’s a good reason why there’s so much help online to identify a Loxosceles spider. Unfortunately you get to see some images of nasty wounds when you google Loxosceles. Picmybug won’t show you any of those.
Why do I mention that I’m not showing disturbing pictures in this post? I mean for some of you the spider itself is disturbing. But for this kind of spider, it is important to identify them. They are amongst the few spiders of medical significance. When I say few, it means out of over 50.000 species of spiders, only a few are dangerous to humans. It’s not easy to find a proper number though. Dupérré et al 2023 count 145 species of Loxosceles. All of them are potentially very venomous.
The common suspects when it comes to the most venomous spiders are following, in no particular order.
The genus Latrodectus, the widows, contains 34 species.
Phoneutria, the wandering spiders, 9 species.
Missulena contains 21 species of mouse spiders.
Atrax, the funnel web spiders are 5 species. The related Hadronyche come with 32 species.
Sicarius are called six-eyed sand spiders. There are 21 species. Hexophthalma are closely related to Sicarius and add another 8 species.
That makes a total of 130 others + 145 Loxosceles, so 275 species of medically significant spiders. Give or take, as you know taxonomy is a ever changing matter. Plus of course whatever species are undiscovered or simply overlooked by me. No guarantee at all for my list! 275 out of 50.000 species equals 0.55%. And 52% of all the most venomous spiders belong to the genus Loxosceles.
And yet, there’s a growing number of enthusiast, who keep exotic animals like Loxosceles at home. This, plus globalisation with imports and exports allow animals and plants to conquer new areas. I guess my spider was either in a tourists luggage, or in a delivery of maybe food items from India or Sri Lanka. Any origin is possible, from any continent.
For non-arachnophiles any brownish spider looks the same. But certain details give a good idea of what spider you’re dealing with. For Loxosceles I find a close look at the legs helpful. They are pretty large, straight without thicker parts, and silky. Also the legs are without any color pattern. Almost boring I must say. They don’t have large visible spines like an orb weaver or a lynx spider for example.
And then there’s the dark pattern in the shape of a violin on the cephalothorax. When you see the spider looking up, the violin is upside down, with the bottom facing the spiders eyes. There are only six eyes, but you need to look really close to count them.
They belong to the family Sicariidae, who’s members all have 6 eyes. So Loxosceles, Sicarius and Hexophthalma are one family. Their members then make 63.3% of the venomous spiders in my list. I wasn’t able to figure out which species I found. The violin is only half the size of the carapace, that’s why I am not sure if it is reclusa. L. rufescens, the mediterranean recluse spider is known as one of the most invasive spiders globally. Could be it.
When a Loxosceles spider got to bite you, it might happen to be dry bite with no further effects. It might as well give you loxoscelism. That means you get necrosis, a tissue destroying condition. Interestingly conditions due to venomous bites or stings are often called after the genus of animal, for example latrodectism, crotalism, bothropism or tetradotoxism.
From what I read it seems Loxosceles prefer dark and dry places, like under tree bark, or in caves. And that might be the reason they sometimes visit us in our homes. Like the one I photographed. Apart from the modern amenities, we’re still cavemen, aren’t we. And thus we also still have arachnophobia. Or at least an unpleasant feeling when we see a spider. With so little potentially harmful species, I can’t imagine this is the whole story though. I asked meta AI. For snakes at least 10% of the species are considered medically significant. Scorpions, bacteria, amphibians, even plants and also fishes would have 1 to 4% or more harmful species. Insects have a similar number to spiders, less than 1%. Following the logic of probability, we should be more afraid of fishes or frogs than spiders. Psychology is an interesting thing.
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