Misconception Monday – Do all spider bites leave two fang marks?

Many people think that the characteristic mark of a spider bite is two symmetrical marks in the middle of a bite. Sort of like this (Note: do not search for “spider bite” under Google Images if you are easily grossed out):

Spider bite or not?

Well, I’m here to set the record straight. Yes, spiders do have fangs at the tips of their chelicera that they use to bite and inject venom into their prey (See: How Stuff Works – Spider Venom). Therefore, it is possible that if a human received a spider bite, there would be these distinctive fang marks. However, the reality is that spiders rarely bite humans at all, and if one did bite, most spiders are likely too small to ever leave two fang marks that are clearly visible to the human eye. In addition, two side-by-side marks are not always indicative of a spider bite. Many arthropods (ants, mosquitoes, biting flies, etc.) can bite more than once, leaving marks that might look like two fang marks to us, but really are two separate bites. Because of this, spiders can certainly be wrongly accused of biting humans much more than they actually do (on the other hand, if the spider is small enough, it could get away with it!)

The easiest way to tell if a bite is from a spider or not is to catch the perpetrator in the act. Unfortunately, once you notice a bite, it is usually too late. If you are really worried that you’ve been bitten by one of the few dangerous spiders out there, then there will be other symptoms to look for (see Mayo Clinic description of symptoms of deadly North American spiders).

Pain, numbness, itchiness, or swelling could all be the result of an allergic reaction to whatever bit you, or could be the result of a bacterial infection at the site of the bite. Whether it is a spider bite or not, if you are experiencing symptoms that are causing you much pain or discomfort, you should see a doctor.


5 thoughts on “Misconception Monday – Do all spider bites leave two fang marks?

    1. Hi Yoanna. I can’t be sure of what bit you without any pictures, or without knowing what part of the world you live in. If the bite is causing any serious health problems, then you should not hesitate to visit a hospital.

  1. I was brushing my teeth this morning in my flip flops around 10am when I felt a sting on my right foot. It was on the right side of the 2nd phalanges, and on the joint before the nail.

    I winced and took my foot out of the flip flop and rubbed it on my left calf to ease the pain for a second. I finished rinsing and looked down and saw a tiny pink wound. Still into my teeth, I finished up and a minute later looked down and saw there was a little blood and two marks about 1-2 mm away from each other. I dabbed it with my finger, squeezed the inexplicable wound, and made a new red dot appear. I noticed my epidermis was torn a bit. I splashed alcohol on it which was WAY more painful than the initial injury.

    It’s now 12+ hours later and it’s still sore but that’s about it. The wound is still pink, but already congealed and in repair mode. I’ve been on my bare feet all day inside, and both feet are tired, with the injury foot only slightly more achy (that might have to do with how I shift my weight when I stand, though).

    After researching other sites and here, I have concluded I was bitten by a horsefly in more likelihood than a spider. The tiny bit of torn epidermis was the deciding factor. A couple of flies that had gotten in after I let the dogs out.

    Thanks for the article!

      1. Yeah, thanks! That fly went Edward Scissorhands on the second bite for sure. I read about a man who died very fast after a horsefly bite, but evidently his was a rare, sad reaction. Luckily, mine is but a small scab now.

        I forgot to add in my original post that minus the intense color and a bit more shredding (ha), my bite looked just like the one in the picture.

        Thanks again for helping me figure it out!: šŸ™‚

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