The animal or insect brain is principally a center of association between significant sense organs of the head and different body regions. But do insects have brains practically? If you have the same question about an insect’s brain and want to know its details and anatomical facts, then continue this article.
Quick answer: yes, insects have a very complex brain located in the head, just dorsal to the esophagus. There are 3 distinct lobes in the insect’s brain from dorsal to ventral – protocerebrum, deutocerebrum, and tritocerebrum.
If you compare insect brains with mammals, you will find a significant variation in their structure. Here, I will show you the main anatomical facts of an insect’s brain so that you may compare it with other animals’ brains.
Do insects have brains?
Like other animals, an insect’s brain is also the principal association center of the body. It links significant sense organs located on the head and motor neurons of different body regions.
But do insects have a similar structure in their brains? In most parts of the insect brain, you will find the mass of neuropile tissue. You may also find the below-mentioned contents in the mass of the insect brain –
- The root of the nerve from compound eyes and ocelli,
- Various sense organs from the antennae and preoral cavity,
- Nerve tracts from subesophageal ganglion, and
- Ganglia of the ventral cord in the thorax and abdomen,
Thus, it is believed that the insect brain is necessary for the initiation of all activities. Again, this initiation is stimulated by the cephalic sense organs of the specific insect.
An insect has no voluntary activity, but the vital function can continue until the body tissue remains alive. You will also find some motor neurons in the different regions of the insect’s brain.
Motor neurons in the antennae muscles are also present in the insect brain. But as I told you before, most of the nerve cell bodies found in insect brains belong to interneurons.
Some of these neurons are concerned with the integration of activities. Constant, other interneurons extend down the nerve cord to the posterior ganglia.
The structures of the insect brain (interneurons and motor neurons) control their behavior. Let’s see the different segments of an insect’s brain with their exciting features.
Insect brain anatomy
The external appearance of the brain from different insects varies, but it always shows 3 successive segments. You may easily differentiate these 3 segments from the internal structure of the insect brain.
In older insects, you will find the below –mentioned 3 lobes (shown in Table 1) in its brain –
| Insects Brain | Lobes of Insects Brain |
| Forebrain of Insect | Protocerebrum |
| Midbrain of Insect | Deutocerebrum |
| Hindbrain of Insect | Tritocerebrum |
Now, let’s see the labeled diagram of the insect brain; here, the first and largest lobe is the forebrain of the protocerebrum. Then, the second lobe of the insect brain is the midbrain or deutocerebrum.
Finally, the third lobe of the insect brain is the hindbrain or tritocerebrum. Again, the lateral lobes of the protocerebrum and deutocerebrum are united by internal commissural tracts.
In addition, the tritocerebrum of the insect brain is generally connected with the other lobes by a free nerve trunk (suboesophageal commissure).
You will see the different structures, segments, or cell masses in an insect’s brain’s first largest lobe (protocerebrum). In the next section of the guide, I will discuss these cell masses or structures from the protocerebrum.
Lobes of an insect brain
So, from the above discussion, you may come to know there are 3 distinct lobes in most the insect species –
- #1. Protocerebrum – forebrain,
- #2. Deutocerebrum – mid-brain, and
- #3. Tritocerebrum – hindbrain,
Here, the protocerebrum or forebrain is an insect brain’s largest and more complex lobe. In the anatomical features of the protocerebrum of an insect brain, you will find the below–mentioned distinct cell masses and regions of neuropile –
- Optic lobes – the lateral extension of the protocerebrum. It receives sensory input from the compound eyes.
- Ocellar center – is associated with the base of the ocelli’s nerves,
- Central body – is the neuropile and connects the right and left lobes of the protocerebrum. This central body of the insect mainly receives axons from the different segments of its brain.
- The protocerebral bridge (pons cerebralis) – is a mass of neuropile that locates the medial aspect of the central dorsal body,
- Pars intercerebralis – possesses 2 groups of neurosecretory cells and locates in the dorsal median area of the protocerebral bridge or pons cerebralis,
- Corpora pedunculata – this masses possess a central stalk and locates at the side of pars intercerebralis,
This is a very short guide on the protocerebrum of the insect brain. But, you will find a details guide on the anatomical facts of the protocerebrum of an insect brain.
Again, the deutocerebrum is the second lobe of the insect brain that contains the antennae or olfactory lobes. You will see 2 divisions in each lobe of the deutocerebrum of an insect brain.
The tritocerebrum is the insect brain’s smallest lobe and is located beneath the deutocerebrum. You will find both the sensory and motor elements in the connecting tracts of the tritocerebrum of an insect brain.
Do all insects have protocerebrum in their brains?
If you want to learn the details and anatomical facts of the protocerebrum lobe of the insect brain, then you may continue this section. As you know, the protocerebrum is the largest and most complex lobes of the brain; here, I will try to make it simple for your easy understanding.
But, you may have a question – do all insects have protocerebrum in their brains? Well, almost 98% of the insect’s brain shows the protocerebrum lobes along with the other 2 lobes (deutocerebrum and tritocerebrum).
This (protocerebrum) is the most prominent dorsal lobe of cerebral masses of insect brains. You will find mainly the following sub-lobes in the structure of the protocerebrum of the insect brain –
- Lateral protocerebral lobe,
- Median intercerebralis lobes, and
- Ventral accessory lobe (optional),
The neuropile mass of the forebrain (protocerebrum) shows 3 types of structure groups of globuli cells, a cluster of fibers and glomeruli forming bodies, and different fibrous tracts.
Here, the globuli cells of the insect forebrain are the small specialized cells that possess chromatic nuclei. Various insects’ brains have different arrangements and distribution of the globuli cells in the forebrain.
Now, the fibrous and glomerulus masses of the insect’s forebrain (protocerebrum) possess the following features –
- Median dorsal pons cerebralis,
- Dorsal corpora pedunculata,
- Corpora centrale,
- Ventrolateral corpora ventralia, and
- Dorsal corpora optica,
The optic center of compound eyes connects with the protocerebrum of the insect’s brain. You know this optic center locates on the optic lobes of the protocerebrum. An ocellar center is also located at the outer end of the ocellar pedicles.
Now, you will know these structures, as mentioned above in short, from the forebrain of an insect. Here, you may take the example of the Grasshopper brain as the common insect.
Pons cerebralis of an insect brain
This is also known as the Protocerebral Bridge of the insect brain. It lies in the dorsal and caudal segments of the pars intercerebralis (describe this term before).
In the structure of pons cerebralis (Protocerebral Bridge), you will mostly find glomerular types of cells. This structure connects with axons from various segments of the insect’s brain except for corpora pedunculata.
In most insects’ brains, the pons cerebralis possess two masses of dorsal globuli cells.
The central body of insect brain
The corpora centrale is the central body of the insect’s brain. This structure of the insect brain lies cranio-ventral to the pons cerebralis.
In the central body, you will find several distinct groups of glomeruli cells. These glomeruli together form an oval mass on the long axis.
Do all insects possess similar structures in the central body of their brains? No, you may find a little difference in the structure of the central body or corpora centrale in various insects’ brains.
You will not find any direct connection between nerve fibers with the central body of the insect brain. But, some axon fibers from various segments of the insect brain may connect with the central body.
Corpora pedunculata of insect brain
The corpora pedunculate bodies of the insect’s brain are also known as the mushroom bodies. These pedunculate bodies are located in the dorsal part of the brain between the protocerebral lobe and pars intercerebralis.
Each of the bodies consists of the following –
- An expanded cap in the upper part of the insect brain,
- A mass of globuli cells, and
- The large, thick, and fibrous stalk (pediculus extends forward),
In the cellular cap of the corpora pedunculate bodies, you will find the lateral groups of globuli cells. These globuli cells of the cellular cap may divide into 2 sub-groups in some of the insect’s brains.
Axons from the globuli cells give off short arborizing collaterals. These collaterals form a synaptic association with other incoming fibers and the other brain parts.
Corpora ventralis of an insect brain
It is the ventral part of the protocerebrum of the insect brain. This structure lies in the ventrolateral aspect of the insect brain.
The corpora ventralis communicate protocerebrum and deutocerebrum by a transverse commissural tract. This tract passes beneath the central body, and the median root of corpora pedunculate.
You will see the connection of this corpora ventralis with other different segments of the insect’s brain. The anatomical features of these ventral bodies may vary in different insect species.
Optic centers of insects brain
The corpora optica is not part of the insect brain. You know the optic bodies or corpora optica are the association center of both ocelli and the compound eyes.
Again, the optic centers are the ganglionic centers of the lateral eye of an insect. It contains the optic lobes and has a close association with the protocerebrum of the insect’s brain.
You will see the optic nerve that possesses the short retinal fibers from the insect’s eye to the optic lobe of the brain. Generally, there are 2 ganglionic bodies in each optic lobes – a distal lamina ganglionaris and a proximal medulla surrounded by the ganglion cells.
You may also find a great variation in the anatomical features of the optic centers of different insects. The optic centers of insects are the most intricate nervous mechanism.
Ocellar centers of an insect brain
The ocellar centers of facial ocelli lie in the distal part of the ocellar pedicels. Here, the fibers from the ocellar center enter the lower part of the insect brain.
Now, they become associated with the terminal branch from the optic tract of the insect’s compound eyes. You may see two strands of fibers in the pedicel of the median facial ocellus.
Deutocerebrum of an insect brain
Deutocerebrum is the second part of the insect’s brain that contains the center of the antennal nerves. It actually contains the antennal lobes (olfactory) and the antennal mechanosensory and motor enter.
You will also find the poorly defined region of neuropile and dendritic arborization of the motor neuron. And you know, the dendritic arborizations of motor neurons control the muscles of an insect’s antenna.
Here, the sensory nerve fibers of the antennal nerve trunks terminate in numerous glomeruli. And these glomeruli distribute mainly in the periphery of the deutocerebral neuropile.
Again, the ganglion cells of the motor fibers attach to the antennal muscles. These ganglion cells lie in the lateral parts of the deutocerebral lobe of an insect’s brain.
A fibrous deutocerebral commissure connects the antennal glomeruli of both sides of the insect. This structure traverses the lower part of the insect brain.
Tritocerebrum of insect brain anatomy
A small part of the insect brain consists of pairs of lobes beneath the deutocerebrum. This tritocerebrum is usually evident as a pair of swelling or distinct lobes.
From this tritocerebrum of the insect brain, circumesophageal connectives pass to the subesophageal ganglion. The tritocerebral lobes of either aspect are connected by the commissure passing behind the esophagus.
The main nerves of the tritocerebrum in an insect are the frontal ganglion connectives. Sensory and motor elements connect the frontal ganglion of the tritocerebrum and the labrum.
The unique features of the tritocerebrum segment of the insect brain are –
Have a connection with both suprastomodaeal parts of the nervous system,
Do insects have nerves in the brains
If you are a student of entomology, you might learn the details of the anatomical facts of an insect’s brain. Then, you might learn the different nerves that have a connection with the insect brain.
But do insects have nerves in their brains? Well, the main nerves of the insect brain are the nerves of a compound or simple lateral eyes, dorsal ocelli, antennae, and labrum. Let’s see what the major nerves that have a great connection with the insect’s brain are –
- Nerves opticus – these are the true nerves of a compound or simple lateral eyes of the insects,
- Nervi ocellarii – these are the slender ocellar pedicles that unit the facial ocelli with the insect brain,
- Nervus ganglii occipitalis – this is the short and slender nerve that arises from the back of the insect brain and passes to the occipital ganglion,
- Nervus antennalis – this is the antennal nerve of the insect, which root may find in the deutocerebrum segment of the brain,
- Nervus tegumentalis – this is a dorsal tegumentary nerve that arises from the caudal and lateral aspect of the insect brain,
- Nervus lateralis – this is the nerve in the insect that arises from the lateral aspect of the brain,
- Nervus labrofrontalis – this is a short nerve trunk that arises from the tritocerebrum segment of the insect brain,
- Nervus subpharyngealis – a small pair of nerves that arise from the suboesophageal tritocerebral commissure,
There are some other small nerves in the insect brain (originating from the brain or surrounding structures). You will find more information on insect brains with labeled diagrams on social media of insect pet.
Frequently asked questions on insect brains
Now, let’s see the common inquiries on insect brains that people love to ask. Here, I will enlist the most common questions on insect brain anatomy that insect lovers ask.
Okay, let’s see the enlisted questions with their concise answers below –
Do arachnids have brains?
Yes, arachnids (for example – spiders) have a well-defined brains. Though a spider is not a true insect, you may find a similarity in the structure of the brain with the insect.
These arachnids possess a big brain which also has 3 well-segmented areas.
Do all animals have brains?
Almost all animals in the world have well-defined brains. But few animals in the world don’t possess any brains.
You will not find any brain in jellyfish, starfish, sea spongy, and others.
Do insects have hearts?
Yes, the insects have hearts that help mediate hemolymph circulation around its body. Here, the circulation system of the insect is open. Thus, hemolymph is in direct contact with the insect organs.
Do insects have blood?
Yes, the insects have blood (hemolymph) which accounts for 10 – 25% of the volume of the insect. You will find inorganic ions, sugar, amino acid, and other organic compounds that maintain the osmotic pressure.
Do insects have feelings and thoughts?
Some larger and smaller insects in the world have great feelings and thoughts. They may be depressed by stress and become active in certain situations.
Can insects feel pain?
Different entomologists proved that insects also feel pain, known as nociception.
Do insects have a memory?
Research revealed that small to larger insects have a good memory. As they possess a well-developed nervous system and brain, the memory system of these insects is almost similar to other animals.
Do small and stick insects have brains?
Yes, all the small and stick insects in the world have brains. They also possess 3 well-defined segments in their brain (both small and stick insects).
But, you may find a little difference in the structures of the protocerebrum and tritocerebrum segments of the smaller insects.
Can insects get brain damage?
Several studies have been performed on insect brain damage (especially on flies’ brains). The results of these studies showed that insects get brain damage.
Conclusion
So, you got the answer to your inquiry – do insects have brains? All the insects of the world possess a well-defined small brain in their head.
Almost all insects show 3 defined segments in their brain – protocerebrum, deutocerebrum, and tritocerebrum. The labeled diagram on insect brain anatomy might help you understand the basic features of all insect brains.
