Page 104 - Miracle in the Eye

The wide visual perspective of a fly's eyes.

tion from each ommatidium is then combined, like pieces of a mosaic, to form
a single image of the outside world. The higher the number of ommatidia, the
keener the vision becomes, with each unit contributing a different part of the
complete picture. 35
The head of the common housefly is dominated by a pair of large com-
pound eyes containing approximately 4,000 ommatidia. In wingless insects
such as female fireflies there are 300 ommatidia, 5,100 in mayflies, 9,000 in
yellow-winged coleopterans and between 10,000 and 28,000 in dragonflies
and damselflies.

A Visual Range of 360 Degrees
The housefly's eye contains 4,000 small, simple ommatidia which can be
moved at will. Since each ommatidium faces a different direction, the fly is
able to see to the front, back, left, right, top and bottom, giving it a 360 degree
perspective of the world.

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