Do Insects Have Brains?

Written by Taiwo Victor
Published: February 22, 2022
Image Credit iStock.com/gan chaonan
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Most insects have tiny bodies. Some don’t even grow beyond a centimeter. Because of this, many people can’t help but wonder if insects have brains. And if they do, what do they use them for? When you are about to swat a fly or a cockroach, it often evades your motion, indicating that they have minds and senses. But when you smack a mosquito, you cannot see anything apart from the blood that they might have sucked out from you. Some insects, like cockroaches, can even survive for a few more days with a severed head, which may imply that their brains are not as significant as human brains. Apart from the mere question of having a brain, we also can’t help but wonder, are insects intelligent? There are plenty of questions to ask when it comes to insects and intelligence. This article will delve deeply into the insect brain and its vital role in the insect’s life.

Do Insects Have Brains?

Louse
Though insects brains don’t work the way humans’ do, but they have brains.

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It might come as a surprise to many, but insects do have brains. However, the insect brain does not work as significantly as the human brain does. The notion about cockroaches and other insects living for a few more days without a head is entirely accurate, and this happens because roach heads do not possess a mouth and a nose. They also do not need their brains to breathe as cockroaches breathe via tiny holes in their bodies, called spiracles. This indicates that cockroaches can continue breathing for a few more hours or days without a brain. 

However tiny they are, insects have brains, but they are not as functional as ours are. Some insects can survive without a head because they do not bleed excessively like humans and other warm-blooded animals when their heads are severed. Insects do not have blood. They have hemolymph, a liquid substance that circulates throughout an arthropod or other invertebrates bodies that remains in direct contact with their tissues. In other words, it is the equivalent of human blood. 

Inside an Insect’s Brain

Rarest Butterflies in the World
Insects have little brains spread throughout their bodies called ganglia.

pixelworlds/Shutterstock.com

Insects have small brains inside their tiny heads. Apart from this central brain, they also have little brains spread throughout their bodies, known as “ganglia.” Like us, insects have a nervous system that helps them see, move, and sense things. Their nervous systems are composed of a series of ganglia that provide nerves to other segments of their body. Brains of insects are located at the back of their heads, consisting of three parts or pairs of lobes:

  • protocerebrum
  • deutocerebrum
  • tritocerebrum

These lobes have ganglia or little brains, fused with clusters of neurons that vary in number depending on the insect species. Fruit flies, for instance, have 100,000 neurons, while honey bees have around 1 million neurons. If you think that is too many, you can compare that to a human brain’s 86 billion neurons. Yet, since insects are way smaller than humans, their senses and reflexes are faster. Insect brains help them see, smell, taste, and sense things way faster than us, which is why insects move quicker, especially in the face of danger. So if you are wondering why insects can be so hard to kill, blame it on their brains!

The Three Lobes of an Insect’s Brain

As mentioned above, the insect brain has three pairs of lobes. They are infused with ganglia that process sensory information, and each has its different use. The first lobe, the protocerebrum, is connected to the compound eyes and the ocelli. Ocelli are light-sensing organs that let insects catch sight of movements. The cluster of neurons inside this lobe composes the insect’s central brain. This lobe is composed of mushroom bodies comprising three regions –calices, peduncle, and alpha and beta lobes. 

Calices – It acts as a receiving area for incoming data.

Peduncle – The peduncle sends information to the alpha and beta lobes.

Alpha and Beta Lobes – The output region transmitting the data to the body.

The brain’s second lobe, the deutocerebrum, supplies nerves to the insect’s antennae. The insect can collect odors, taste, tactile sensations, and even temperature or humidity via their antennae. The insect’s antennae that you often notice moving around with its every move connects to its brain. The nerves that the deutocerebrum lobe supplies to the antennae are critical because it helps insects sense things in their environment.

The third lobe, the tritocerebrum, is connected via neurons to the insect’s upper moveable lip, combining the sensory information coming from the two other lobes. This lobe also connects the brain to the insect’s stomodaeal nervous system, which supplies organs with nerves. The tritocerebrum also acts as a sub-brain for the insect’s body, allowing it to survive a while longer without a head.

Are Insects Smart?

Types of beetles - Stag beetle
The protocerebrum lobe in insects account for memory and learning.

iStock.com/KarelGallas

You might think that insects must be intelligent, knowing almost your every move. Whenever you try to swat a fly or kill a bug, cockroach, or mosquito, you need to act stealthily to catch them. More often than not, insects will still sense your movements no matter how quiet you think you are moving. Yet, insect intelligence is still a wonder to scientists up until now. Studying insect brains means comparing human intelligence to their minds. But by doing that, scientists must break down their minds from a human perspective. Despite the lack of scientific data, it is apparent that insects are indeed smart. 

Insect brains can create memories, keep them, and make wise decisions. The protocerebrum lobe accounts for memory and learning, which equates to intelligence. However, bigger brains in the insect world don’t necessarily mean smarter moves. Some insects are known to be smarter than others because of how they adapt to an environment. 

Since various ganglia or little brains throughout insects bodies may remain with them even after their heads are cut off, they can still control other functions not governed by their central brain. This includes locomotion, reproduction, salivary glands, and neck movements.

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