Besides their large compound eyes,insects have another organ that is sensitive to light,
Called the ocellus,this organ has an eyelike structure but does not sense true images.
Rather, the ocelli respond to-changes in light intensity,by stimulating the insect to increase or decrease its activity.
During the larval stage of development,the ocelli in most insects are lateral-that is,located on the sides of head.
In most adult insects,the ocelli are dorsal -on the top or back of the head.
Eyes and ocelli:
The locust has three ocelli between its eyes.
The ocelli and insect activity:
The stimulation of light falling on the ocelli makes walking insects walk faster and flying insects fly faster.
Blackout:
If all of the ocelli are covered,the insect will not move towards a bright light.
Slowdown:
A locust with its centre ocellus covered walks slower than normal,at 2.5 centimetres per second.
All system go:
With all ocelli open to the light,a locust walks toward the light at a speed of 4 centimetres per second.
Ocellus varieties:
The majority of adult insects have three ocelli, arranged in a triangular pattern on the fore head.
The centre ocellus is believed to be two fused primitive ocelli,in structure it is similar to the eyes of dragon flies and honey bees.
The ocelli develop when the wings do,and most wingless insects have no ocelli.
Nocturnal moths also lack this light sensitive organ.
The structure of the ocelli varies greatly from species to species.
The ocelli influence not only an insect's flying and walking speed but also its general level of activity.
Compared with normal honeybees,a bee with its ocelli covered begins gathering food later in the morning,when sunlight is brighter and returns to the hive earlier in the evening.
A housefly with its ocelli darkened will not move at all,even in daylight.Other flies with their ocelli obscured react only slowly to changes in light intensity.
A honeybee with its ocelli covered starts work later in the day and quits eatlier than normal.
Flies with their ocelli blackened remain motionless during the day.
Called the ocellus,this organ has an eyelike structure but does not sense true images.
Rather, the ocelli respond to-changes in light intensity,by stimulating the insect to increase or decrease its activity.
During the larval stage of development,the ocelli in most insects are lateral-that is,located on the sides of head.
In most adult insects,the ocelli are dorsal -on the top or back of the head.
Eyes and ocelli:
The locust has three ocelli between its eyes.
The ocelli and insect activity:
The stimulation of light falling on the ocelli makes walking insects walk faster and flying insects fly faster.
Blackout:
If all of the ocelli are covered,the insect will not move towards a bright light.
Slowdown:
A locust with its centre ocellus covered walks slower than normal,at 2.5 centimetres per second.
All system go:
With all ocelli open to the light,a locust walks toward the light at a speed of 4 centimetres per second.
Ocellus varieties:
The majority of adult insects have three ocelli, arranged in a triangular pattern on the fore head.
The centre ocellus is believed to be two fused primitive ocelli,in structure it is similar to the eyes of dragon flies and honey bees.
The ocelli develop when the wings do,and most wingless insects have no ocelli.
Nocturnal moths also lack this light sensitive organ.
The structure of the ocelli varies greatly from species to species.
The ocelli influence not only an insect's flying and walking speed but also its general level of activity.
Compared with normal honeybees,a bee with its ocelli covered begins gathering food later in the morning,when sunlight is brighter and returns to the hive earlier in the evening.
A housefly with its ocelli darkened will not move at all,even in daylight.Other flies with their ocelli obscured react only slowly to changes in light intensity.
A honeybee with its ocelli covered starts work later in the day and quits eatlier than normal.
Flies with their ocelli blackened remain motionless during the day.
