Why do tarantulas have blue blood?

Question

Why do tarantulas have blue blood?

Answer 1

What makes you think that?  It is NOT blue, it's clear, and it flows throughout the body, something like an interior wash, not through veins like in humans.

I don't know of any insect or Arachnid that has "blue" blood.

Answer 2

In humans the oxigen is bound to hemoglobin,

a molecule that contains iron and beeing red gives

that colour to the blood. In spiders, and  in

many other arthropods (as crustaceans)  and also in

most mollusks the oxigen is bound to a different

molecule called hemocyanin that contains copper

instead of iron.

The hemocyanins  are proteins colourless in the

reduced or deoxygenated state but the oxydized

copper beeing  blue/green, gives that colour to

the oxygenated blood.

Therefore...spiders have "blue"  blood...

Answer 3

They're oxygen transport mechanism is based on copper. Not iron. Iron makes it red. Copper makes it blue.

Good luck.