Give Now

A Moment of Science

Why Is Insect Blood Green Or Yellow?

You've probably heard someone use the phrase "blood red," but have you ever wondered if all blood really is red in humans?

insects pinned to a board

Photo: Jeremy Brooks (Flickr)

Insects have different colored blood compared to humans.

You’ve probably heard someone use the phrase “blood red,” but have you ever wondered if all blood really is red? For example, think about the bugs you’ve seen splatter against your car’s windshield, leaving behind a clear, yellowish, or greenish liquid. That liquid, is hemolymph, or insect blood.

Insect Blood

The blood of an insect functions differently than the blood of a human. In humans, blood gets its red color from hemoglobin, which travels through blood vessels carrying oxygen from the lungs to the rest of the body. Insect blood, however, does not carry gasses and has no hemoglobin. Instead, bugs have a system of tubes that transport gasses directly between their cells and the outside air.

In fact, insects don’t even have blood vessels. Instead there is a hollow space inside their external skeleton in which their blood oozes around. This cavity extends to the antennas, legs, and wing veins. The bug’s heart, a long tube that stretches the length of its body, pushes the blood from the rear end of the insect on forward. The bug may also have little hearts at the ends of its extremities to help move the blood along.


Pumping blood is a slow process: it takes about eight minutes for an insect’s blood to circulate completely. Like human blood, bug blood carries nutrients and hormones to the insect’s cells. The greenish or yellowish color of insect blood comes from the pigments of the plants the bug eats.

  • DianeNess

    “The greenish or yellowish color of insect blood comes from the pigments of the plants the bug eats.”

    This is bad science and you should be deeply ashamed. Hemolymph itself, the insects’ “blood” lends the yellowish color, while hemocyanin, the oxygen-transporting copper-based complex in the higher arthropods lends the greenish color.

  • caters

    No actually green blood comes from hemoglobin that has been broken down slightly. This is the case in some reptiles which is why you might see green blood when a reptile is bleeding. That hemocyanin give blood a blue color and is why if you look at a crab’s blood, it looks blue.
    Hemolymph is very similar to our lymph. It is itself a clear fluid that looks a lot like water and has nutrients. So the pigment in insect blood must come from something besides hemolymph.

  • akshaya

    what does oozes mean????

Stay Connected

What is RSS? RSS makes it possible to subscribe to a website's updates instead of visiting it by delivering new posts to your RSS reader automatically. Choose to receive some or all of the updates from A Moment of Science:

Support for Indiana Public Media Comes From

About A Moment of Science

Search A Moment of Science