2007-03-12 04:59:26 · 3 answers · asked by Yashwant M 1 in Science & Mathematics ➔ Zoology
The eye of cockraoach is called compund eye because it is composed of thousands of units called ommatidia( singular: ommatidium). Each ommatidium is cylindrical( a bit conical), covered by iris pigment sheath and retinal pigment sheath. These sheaths contain pigments. These pigments are spread out along the pigment sheaths when there is a bright light. Thus ommatidium becomes covered from sides preventing light from entering from sides. The light which falls vertically is allowed to form image. In this way for each ommatidium one image is formed. And,there are as many image as there are ommatidia. This type of vision is called mosaic vision( apposition). This happens in bright light.
In dim light, however, the pigments of these sheaths are concentrated at one place allowing light to come in from sides. In this case a superposition image is formed. Thus pigments help in the formation of two kinds of images: apposition and superpostion.
2007-03-15 00:19:26 · answer #1 · answered by Ishan26 7 · 0⤊ 0⤋
It is the eye within an eye. They have one eye which is divided into 25 or more eyelets. The eyelets contains small black pigments
2007-03-14 02:43:57 · answer #2 · answered by Shreyan 4 · 0⤊ 0⤋
Go to answers.com at search of site type Blattodea (Cockroaches) , you will get all the details you need to know about them.
2007-03-12 13:24:44 · answer #3 · answered by Richard J 6 · 1⤊ 0⤋