Do Insects Have Hearts or Blood?

Insects are tiny, so it can be hard to imagine that their bodies contain whole organ systems – but they can! Just like other animals, insects have a circulatory system that delivers nutrients to all the cells of their bodies. However, the anatomy of the insect circulatory system is very different to that of your own. So, do insects have a heart? What color is insect blood? And what is the anatomy of insect circulatory systems?

Do insects have hearts?

Insects do have hearts, which they use to pump haemolymph around their bodies. Haemolymph is the insect version of blood, and it delivers nutrients to all the cells of the bug’s body. The function of the insect heart is similar to that of your own, but the anatomy of their circulatory system is very different to the vertebrate version.

What is insect blood, and what color is it?

Insects have their own version of blood, called haemolymph. The main difference between blood and haemolymph is that blood contains red blood cells, and haemolymph does not. This is because haemolymph does not transport oxygen, which is the main function of red blood cells in vertebrates. Instead, insects take in oxygen through spiracles; tiny openings in the insect exoskeleton. Oxygen diffuses through the spiracles and into tubes called trachea, which carry it throughout the insect’s body.

Haemolymph also contains a higher proportion of plasma than blood does. Just over half of the total volume of human blood is plasma, but this watery fluid constitutes around 90% of the insect haemolymph.


Thanks to its lack of red blood cells, haemolymph is not red like vertebrate blood. Haemolymph is mostly water, so it is usually clear. However, it may also contain pigments that give it a green or yellow tinge.

The insect circulatory system

The biggest difference between the insect and vertebrate circulatory systems is that insects have an open circulatory system, and vertebrates have a closed circulatory system.

In a closed circulatory system (like the ones humans have) blood is transported around the body in blood vessels. Blood is pumped through the arteries and veins by the heart, and delivers oxygen and nutrients to all the cells of the body.

Insects have an open circulatory system, which means their haemolymph is not enclosed in blood vessels. Instead, the insect heart pumps haemolymph into a cavity called the hemocoel, where it circulates around the insect’s organs and delivers oxygen and nutrients to the tissues.

What does the insect heart look like?

The insect circulatory system includes a heart, which pumps haemolymph around the insect’s body. However, the anatomy of the insect heart is very different to that of your own.

Haemolymph in insects is circulated by a tubular structure called the dorsal vessel, which is found in the hemocoel and runs down the length of the insect’s body. The dorsal vessel is the ‘heart’ of the insect.

It is divided into chambers that are separated by valves, which prevent haemolymph from flowing backwards.

Muscles in the walls of the dorsal vessel contract to squeeze haemolymph from chamber to chamber. At the head end of the insect, a simple tube called the aorta empties haemolymph near the brain. The haemolymph bathes the brain and the internal organs as it circulates through the hemocoel, before eventually re-entering the heart at the hind end of the insect’s body.

What is the heart rate of an insect?

The insect heart rate can vary a lot between species, but is typically somewhere in the range of 30 – 200 beats per minute.

Can an insect have a heart attack?

Insects have circulatory systems containing a heart and ‘blood,’ just like we do. However, there are still lots of differences between the insect and invertebrate circulatory system, and one is that they are vulnerable to different diseases.

Insects can not get heart disease, and they can’t have heart attacks. A heart attack happens when fatty deposits build up in the coronary arteries and prevent oxygenated blood from reaching the heart muscle. This can cause damage or even death of some or all of the heart muscle.

Jennifer Murray/

Insects have an open circulatory system (meaning their blood is not contained in blood vessels) so they don’t have arteries for fatty deposits to accumulate in. Insect haemolymph also does not transport oxygen, so the heart is not dependent on blood flow for oxygen. Instead, oxygen reaches the heart muscle via the insect’s trachea. If the trachea were to become blocked, the insect might experience something like a heart attack because oxygen would not be able to reach the heart muscle.

However, this doesn’t mean that insects can’t get sick. Bugs can get diseases just like humans do, and can be infected by bacterial, fungal, parasitoid, and viral pathogens. These can cause a variety of deadly illnesses in insects, some of which may affect their circulatory system.


All animals have a circulatory system, which they use to transport oxygen and nutrients to all the cells of the body. Insects are no exception to this rule, but the anatomy of the insect circulatory system is very different to that of vertebrates.

Insects do have hearts, but they look very different to our own. The insect heart is a long, tubular structure that extends down the length of the insect body, and delivers nutrient-rich blood to the organs and tissues.

Insects also have their own version of blood, called haemolymph. Unlike human blood, insect haemolymph does not carry oxygen and lacks red blood cells. It is mostly made up of a watery fluid called plasma and is usually clear, though it may have a yellow or green tinge.

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