The Better to See You With

Just as people without color vision have a hard time understanding what color is, it is impossible for humans to imagine what it is like to see through the compound eye of an insect. These eyes are made of thousands of tiny rods called ommatidia, each one a small eye connected directly to the brain. Scientists theorize that the insect's brain composes the images received from each ommatidium, enabling it to perceive movement in any possible direction-in some species, even from behind. •

One Eye, or Thousands

Each ommatidium is responsible for a small portion of the visual field. Depending on the type of light they receive, the pigmented cells around each rhabdom can vary their diameter, regulating the overall sensitivity of the compound eye.

.COMPOUND EYE

Field of Vision

A fly's ommatidia are arranged in circles, and each one covers a portion of the field of vision. Such systems may not yield a high-resolution image, but they are highly sensitive to movement. The slightest motion causes a transfer of sensitivity from one ommatidium to another. This is what makes it so hard to catch a fly.

Drosophila sp.

FIELD OF VISION OF A FLY

Sections of field of vision

Perceived path

A Bee's Eye View

Compared with human vision, a bee's vision is somewhat nearsighted. Even the images of nearby objects are blurry. Its compound eyes have some 6,900 ommatidia.

HEADED FOR NECTAR

Sensitivity to ultraviolet light, invisible to the human eye, enables worker bees to find the nectar inside the flowers.

180° field of vision

Binocular field

Human field of vision

£G3

HUMANS

With binocular vision, a flat and undistorted image flAB

BEES

In a larger field, the same image is narrower.

OMMATIDIUM

MOUTH-

The mouth has apparatus for licking and sucking.

VISION

rsrZ y-

-Ommatidia

Antenna f r

PROTECTIVE VISION IN THE ROUND CALCULATORS

The eyelets of the Certain dragonflies have This common blue tachinid fly cover a completely spherical damselfly uses its eyes its eyes. field of vision. to calculate distances.

THE HOUSEFLY HAS

4,000

OMMATIDIA.

RETINAL CELL

PIGMENT CELL

-RHABDOM

Connects each lens with its nerve

LENS

Cone-shaped, to direct light to the rhabdom lE^fl vttkfl

CORNEA-

Hexagonal in shape to fit into the rest of the compound eye

Moving object

Was this article helpful?

0 0

Post a comment