Why Spiders Don´t Bleed Like Humans

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Spiders have very different anatomy compared to us humans. While they have a heart, brain, and so on they don´t have the same blood as we do. Their blood isn´t red and they can use their blood to move their legs.

As a whole, spiders can bleed but their blood is not red and their blood has a different viscosity. Spider blood is called hemolymph. Hemolymph is the circulating fluid in invertebrates that functions similar to blood. But hemolymph is not red it is blue when it carries oxygen or colorless grayish when it doesn´t carry oxygen.

Spider blood has a higher viscosity than our blood. So if a spider is hurt it won´t bleed as a human would. Spiders and other invertebrates bleed much slower than humans.

What Does Spider Blood Look Like?

Even though spiders have hearts, brains, and other intestines that humans also have their blood looks very different and also functions differently than ours.

As a whole, spider blood looks blue or grayish-blue. The blood of a spider is called hemolymph and it uses hemocyanin to transport oxygen. Hemocyanin is colorless when it doesn´t transport any oxygen and it turns blue when it transports oxygen. This results in the blue or grayish-blue color of the blood.

You can read more about Hemocyanin right here on Wikipedia if you want to know more.

But generally, the whole blood circulation system of the spider works very similarly to that of humans with a few exceptions.

For one, humans have red blood cells that are called hemoglobin. These blood cells carry oxygen to the parts of the body where it is needed. Spiders and other invertebrates utilize hemocyanin to transport oxygen instead.

The spider has the ability to raise its blood pressure in select parts of its body to move its legs or to help it during molting to get rid of its exoskeleton.

Do Spiders Have Blood?

I see this question asked a lot and it is often acompanied by stories of killing a spider and discovering that it bled red. So I want to answer this question as best as I can so that there is hopefully no further misunderstanding.

As a whole, spiders have blood but it is blue and not red. Spiders don´t drink human or vertebrates blood. Some humans apear to bleed red when they are killed but that is most likely just red muscle fibre and not red blood.

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