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STRUCTURES OF INSECTS- COMPOUND EYE, OCELLI AND ANTENNAE
COMPOUND EYE- INTRODUCTION:
The compound eye is an eye consisting of many individual lens systems, called ommatidia. Compound eye is present in many members of phylum Arthropoda such as insects and crustaceans. Compound eye contain thousands of ommatidia. Ommatidia are small independent photoreception units that consists of a cornea, lens and photoreceptor cells which can discriminate brightness and color. (Marshall etal, 2003.p.459)
Most of the insects have a pair of large prominent compound eyes, composed of units called ommatidia. A single compound eye may have 30,000 ommatidia, such as in large dragonflies.

Fig 1.1.Compound eye of a dragonfly.
As compared to the single- aperture eye, compound eyes have poor image resolution. The benefit of compound eye is that they possess a very large view angle, have ability to detect fast movements and also detect the polarization of light in some cases. (Volkel,R.,Eisner, M. etal june 2003.p. 461-472)
Types:
There are two types of compound eyes one of them is apposition eyes, that form multiple inverted images, and the other is superposition eyes , that form a single erect image.(Gaten, Edward 1998)
1. Apposition Eyes:
These can be divided into two groups. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. Mantis shrimp is an advanced example of this type of eye.

Fig. 1.2 Apposition eye
Neural superposition eye:
In the other kind of apposition eye, each lens forms an image, and the images are combined in the brain. This type is found in strepsiptera. This eye is also known as the neural superposition eye.

Fig 1.3 Neural superposition eye
2. Superposition eyes:
It is divided into three types
a. The refracting
b. The reflecting
c. The parabolic
a. The refracting superposition eye : It has a gap between the lens and the rhabdom, having no side wall. Each of the lens takes light at an angle to its axis and then reflects it to the same angle on other side. The resultant image is formed at the half of radius of eye, the region where the tips of rhabdom lie. This type is found mostly in nocturnal insects.

Fig 1.4 Refraction superposition eye
b. The parabolic superposition eye: This type is found in mayflies, the parabolic surfaces. In this type the inside parabolic surfaces of each facet focus light from a reflector to a sensor array.

Fig 1.5 Parabolic superposition eye.
c. Reflecting Superposition eyes: Long bodied decapod crustaceans such as prawns, shrimps and lobsters possess this type of eye they use corner mirrors instead of lenses this type is not found in insects.
Good fliers like flies , prey catching insects like dragonflies possess specialized zones of ommatidia that is organized into fovea area that produces acute vision. The acute zone has larger facets and flattened eyes. Thus due to flattening more ommatidia receive light from a single spot and thus produce higher resolution.

Structure of compound eye:
Compound eyes cosists of a few to 28,000 receptors, called ommatidia, that fused into the multifaceted eye.

Fig 1.6 Structure of ommatidium
Structure of ommatidium :The outer surface of each ommatidium is a lens and is one facet of the eye. Below the lens is the crystalline cone. The lens and the crystalline cone are light gathering structures. Certain cells of an ommatidium called retinula cells, have a special light gathering area called rhabdom The rhabdom converts light energy into nerve impulses.

Fig 1.6 The structure of compound eye
Pigment cells surround the crystalline cone, and sometimes the rhabdom, and prevents the light that strikes one rhabdom from reflecting into an adjacent ommatidium. (Miller and Harley , page 255 seventh edition )
Advantage of compound eye :
Many insects form an image of sort but the concept of image formation holds no special importance for most species. The compound eye is much better suited for detecting movements. The movement of a point of light less than 0.1 degree can be easily detected when light successively strikes adjacent ommatidia. This is the main reason that how insects choose moving prey and bees become attracted to flowers. Compound eyes can detect wavelength of light falling in UV spectrum , They can also detect polarized light that help them in navigation and orientation.( miller and Harley p 255)

STRUCTURES OF INSECTS- COMPOUND EYE, OCELLI AND ANTENNAE
COMPOUND EYE- INTRODUCTION:
The compound eye is an eye consisting of many individual lens systems, called ommatidia. Compound eye is present in many members of phylum Arthropoda such as insects and crustaceans. Compound eye contain thousands of ommatidia. Ommatidia are small independent photoreception units that consists of a cornea, lens and photoreceptor cells which can discriminate brightness and color. (Marshall etal, 2003.p.459)
Most of the insects have a pair of large prominent compound eyes, composed of units called ommatidia. A single compound eye may have 30,000 ommatidia, such as in large dragonflies.

Fig 1.1.Compound eye of a dragonfly.
As compared to the single- aperture eye, compound eyes have poor image resolution. The benefit of compound eye is that they possess a very large view angle, have ability to detect fast movements and also detect the polarization of light in some cases. (Volkel,R.,Eisner, M. etal june 2003.p. 461-472)
Types:
There are two types of compound eyes one of them is apposition eyes, that form multiple inverted images, and the other is superposition eyes , that form a single erect image.(Gaten, Edward 1998)
1. Apposition Eyes:
These can be divided into two groups. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. Mantis shrimp is an advanced example of this type of eye.

Fig. 1.2 Apposition eye
Neural superposition eye:
In the other kind of apposition eye, each lens forms an image, and the images are combined in the brain. This type is found in strepsiptera. This eye is also known as the neural superposition eye.

Fig 1.3 Neural superposition eye
2. Superposition eyes:
It is divided into three types
a. The refracting
b. The reflecting
c. The parabolic
a. The refracting superposition eye : It has a gap between the lens and the rhabdom, having no side wall. Each of the lens takes light at an angle to its axis and then reflects it to the same angle on other side. The resultant image is formed at the half of radius of eye, the region where the tips of rhabdom lie. This type is found mostly in nocturnal insects.

Fig 1.4 Refraction superposition eye
b. The parabolic superposition eye: This type is found in mayflies, the parabolic surfaces. In this type the inside parabolic surfaces of each facet focus light from a reflector to a sensor array.

Fig 1.5 Parabolic superposition eye.
c. Reflecting Superposition eyes: Long bodied decapod crustaceans such as prawns, shrimps and lobsters possess this type of eye they use corner mirrors instead of lenses this type is not found in insects.
Good fliers like flies , prey catching insects like dragonflies possess specialized zones of ommatidia that is organized into fovea area that produces acute vision. The acute zone has larger facets and flattened eyes. Thus due to flattening more ommatidia receive light from a single spot and thus produce higher resolution.

Structure of compound eye:
Compound eyes cosists of a few to 28,000 receptors, called ommatidia, that fused into the multifaceted eye.

Fig 1.6 Structure of ommatidium
Structure of ommatidium :The outer surface of each ommatidium is a lens and is one facet of the eye. Below the lens is the crystalline cone. The lens and the crystalline cone are light gathering structures. Certain cells of an ommatidium called retinula cells, have a special light gathering area called rhabdom The rhabdom converts light energy into nerve impulses.

Fig 1.6 The structure of compound eye
Pigment cells surround the crystalline cone, and sometimes the rhabdom, and prevents the light that strikes one rhabdom from reflecting into an adjacent ommatidium. (Miller and Harley , page 255 seventh edition )
Advantage of compound eye :
Many insects form an image of sort but the concept of image formation holds no special importance for most species. The compound eye is much better suited for detecting movements. The movement of a point of light less than 0.1 degree can be easily detected when light successively strikes adjacent ommatidia. This is the main reason that how insects choose moving prey and bees become attracted to flowers. Compound eyes can detect wavelength of light falling in UV spectrum , They can also detect polarized light that help them in navigation and orientation.( miller and Harley p 255)
STRUCTURES OF INSECTS- COMPOUND EYE, OCELLI AND ANTENNAE
COMPOUND EYE- INTRODUCTION:
The compound eye is an eye consisting of many individual lens systems, called ommatidia. Compound eye is present in many members of phylum Arthropoda such as insects and crustaceans. Compound eye contain thousands of ommatidia. Ommatidia are small independent photoreception units that consists of a cornea, lens and photoreceptor cells which can discriminate brightness and color. (Marshall etal, 2003.p.459)
Most of the insects have a pair of large prominent compound eyes, composed of units called ommatidia. A single compound eye may have 30,000 ommatidia, such as in large dragonflies.

Fig 1.1.Compound eye of a dragonfly.
As compared to the single- aperture eye, compound eyes have poor image resolution. The benefit of compound eye is that they possess a very large view angle, have ability to detect fast movements and also detect the polarization of light in some cases. (Volkel,R.,Eisner, M. etal june 2003.p. 461-472)
Types:
There are two types of compound eyes one of them is apposition eyes, that form multiple inverted images, and the other is superposition eyes , that form a single erect image.(Gaten, Edward 1998)
1. Apposition Eyes:
These can be divided into two groups. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. Mantis shrimp is an advanced example of this type of eye.

Fig. 1.2 Apposition eye
Neural superposition eye:
In the other kind of apposition eye, each lens forms an image, and the images are combined in the brain. This type is found in strepsiptera. This eye is also known as the neural superposition eye.

Fig 1.3 Neural superposition eye
2. Superposition eyes:
It is divided into three types
a. The refracting
b. The reflecting
c. The parabolic
a. The refracting superposition eye : It has a gap between the lens and the rhabdom, having no side wall. Each of the lens takes light at an angle to its axis and then reflects it to the same angle on other side. The resultant image is formed at the half of radius of eye, the region where the tips of rhabdom lie. This type is found mostly in nocturnal insects.

Fig 1.4 Refraction superposition eye
b. The parabolic superposition eye: This type is found in mayflies, the parabolic surfaces. In this type the inside parabolic surfaces of each facet focus light from a reflector to a sensor array.

Fig 1.5 Parabolic superposition eye.
c. Reflecting Superposition eyes: Long bodied decapod crustaceans such as prawns, shrimps and lobsters possess this type of eye they use corner mirrors instead of lenses this type is not found in insects.
Good fliers like flies , prey catching insects like dragonflies possess specialized zones of ommatidia that is organized into fovea area that produces acute vision. The acute zone has larger facets and flattened eyes. Thus due to flattening more ommatidia receive light from a single spot and thus produce higher resolution.

Structure of compound eye:
Compound eyes cosists of a few to 28,000 receptors, called ommatidia, that fused into the multifaceted eye.

Fig 1.6 Structure of ommatidium
Structure of ommatidium :The outer surface of each ommatidium is a lens and is one facet of the eye. Below the lens is the crystalline cone. The lens and the crystalline cone are light gathering structures. Certain cells of an ommatidium called retinula cells, have a special light gathering area called rhabdom The rhabdom converts light energy into nerve impulses.

Fig 1.6 The structure of compound eye
Pigment cells surround the crystalline cone, and sometimes the rhabdom, and prevents the light that strikes one rhabdom from reflecting into an adjacent ommatidium. (Miller and Harley , page 255 seventh edition )
Advantage of compound eye :
Many insects form an image of sort but the concept of image formation holds no special importance for most species. The compound eye is much better suited for detecting movements. The movement of a point of light less than 0.1 degree can be easily detected when light successively strikes adjacent ommatidia. This is the main reason that how insects choose moving prey and bees become attracted to flowers. Compound eyes can detect wavelength of light falling in UV spectrum , They can also detect polarized light that help them in navigation and orientation.( miller and Harley p 255)

As compared to the single- aperture eye, compound eyes have poor image resolution. The benefit of compound eye is that they possess a very large view angle, have ability to detect fast movements and also detect the polarization of light in some cases. (Volkel,R.,Eisner, M. etal june 2003.p. 461-472)
Types:
There are two types of compound eyes one of them is apposition eyes, that form multiple inverted images, and the other is superposition eyes , that form a single erect image.(Gaten, Edward 1998)
1. Apposition Eyes:
These can be divided into two groups. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. Mantis shrimp is an advanced example of this type of eye.

As compared to the single- aperture eye, compound eyes have poor image resolution. The benefit of compound eye is that they possess a very large view angle, have ability to detect fast movements and also detect the polarization of light in some cases. (Volkel,R.,Eisner, M. etal june 2003.p. 461-472)
Types:
There are two types of compound eyes one of them is apposition eyes, that form multiple inverted images, and the other is superposition eyes , that form a single erect image.(Gaten, Edward 1998)
1. Apposition Eyes:
These can be divided into two groups. The typical apposition eye has a lens focusing light from one direction on the rhabdom, while light from other directions is absorbed by the dark wall of the ommatidium. Mantis shrimp is an advanced example of this type of eye.

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