Facts about the animal kingdom

Do Insects Have Blood?

Nick A. Romero
By Nick A. Romero, Biologist and environmental educator. August 10, 2023
Do Insects Have Blood?

Insects do not have blood in the same way as have vertebrate animals. This does not mean they do not have a system for transporting nutrients throughout their body and completing various bodily processes. However, these processes are generally less complex because they are less complex animals. Insects are the most diverse group of animals on the planet. Although more than a million have been identified so far, scientists estimate millions more may remain unidentified. They all share certain characteristics, even when it comes to their circulatory system.

At AnimalWised, we ask do insects have blood? We discover the circulatory system of insects, how it is different from other animals and why it is so important.

You may also be interested in: Do Insects Have Hearts?


  1. Do insects have blood, yes or no?
  2. What is hemolymph in insects?
  3. What is the difference between hemolymph and blood?

Do insects have blood, yes or no?

Insects have a circulatory system. It is known as an open-type circulatory system since the body fluid is distributed directly into the body cavities. Although they have a circulatory system, insects do not have veins or arteries. This means their fluid does needs to circulate through different structures. This is why insects have a dorsal tube through which the fluid passes and is distributed throughout the insect's body.

Since insects do not have blood vessels, we can say their circulatory system is less complex than those of vertebrate animals. In addition to anatomical or structural differences, insects do not have blood like other more complex animals, instead possessing a fluid known as hemolymph.

What is hemolymph in insects?

Hemolymph is a fluid that is part of the circulatory system of insects. It can also be found in some other invertebrate animals, such as arthropods and mollusks. Although insects do not have blood, hemolymph is a fluid which is analogous to it. Although it does not transport the same exact elements as in the case of vertebrates, it fulfills very similar important important functions in the insect's body.

Do insects have hearts?

Since the hemolymph needs to be pumped around the body, insects do have hearts. These are very different to the hearts of vertebrate animals, but they perform the same function in their circulatory system. This structure acts as a pumping mechanism in the body of the insect.

The hemolymph is pumped from the back to the front and sides of the body through the dorsal tube or vessel. This dorsal tube or vessel consists of various valves that have openings through which hemolymph flows. The entire body of the insect is irrigated with hemolymph, including the antennae, wings and legs. As with blood in vertebrate animals, this fluid returns to the abdomen area to go back and start the journey again.

There is an important transport function of hemolymph in insects. Various nutrients and hormones circulate through it. It is made up of cells known as hemocytes, which are involved in the immune response in the insect. They engulf invading microorganisms and participate in the coagulation and healing process when there are wounds and in the metabolism of nutrients.

Hemolymph is also part of the process of transporting metabolic waste produced in the insect. This is carried to structures called Malpighian tubules, through which excretion occurs in the animal. In this way, the circulatory system and digestive systems are combined more closely than in vertebrates.

What color is insect blood?

As we have explained, insects do not have blood. Although the blood of vertebrates can change under some circumstances, it is usually some shade of red due to the presence of red blood cells. In insects, the hemolymph does not have a specific color. It is considered colorless in its natural state, although it can have a green or amber hue.

However, the diet of the specific insect can color the hemolymph. Whatever it is they have ingested can cause the fluid to change color. It can have a bluish, yellowish or even dark brown color, something by pigments that insects include in their diet.

There are also certain insects which feed on the blood of vertebrates. For this reason, if you see a squashed female mosquito that has fed, you will see red blood. This is not the hemolymph, but the blood of the animal it has ingested. However, the blood can color the hemolymph red.

Learn more about the bodily functions of insects with our article on the insect tracheal system.

Do Insects Have Blood? - What is hemolymph in insects?

What is the difference between hemolymph and blood?

Hemolymph and blood are similar, but they have certain key differences. In principle, hemolymph does not have the cells known as erythrocytes, the red blood cells typical of vertebrate blood. Unlike blood, hemolymph has a large amount of free amino acids. Although the hemolymph has a large amount of water, the percentage is higher in the blood, being up to 50% in the former and 80% in the latter.

The hemolymph does not carry oxygen to the insect's body, while blood does. This is because the respiration process in these invertebrates works differently. Different animals breathe in different ways.

Insect body fluid also functions as a solvent for various molecules. It serves as a water reserve in cases where the animal is exposed to desiccation. It also has a special role as a hydraulic fluid, for the expansion of the body when the insect completes the metamorphosis process. It is worth mentioning that the hemolymph carries the substances that the insect needs to be able to metamorphose throughout the body. This is the case for animals that go through metamorphosis.

As we have seen, hemolymph is a different fluid from blood. However, like this red liquid, it also fulfills essential functions for insects. It is for this reason, it is considered analogous to blood, but it is not the same substance.

If you want to read similar articles to Do Insects Have Blood?, we recommend you visit our Facts about the animal kingdom category.

  • Brittanica. (2022). Insects. Retrieved from: https://www.britannica.com/animal/insect/Circulatory-system

  • Kanost, M. (2009). Hemolymph. Editor(s): Vincent H. Resh, Ring T. Cardé, Encyclopedia of Insects (Second Edition). Retrieved from: https://doi.org/10.1016/B978-0-12-374144-8.00126-0
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Do Insects Have Blood?