Eyes of an insect with a large increase similar to a small grill.
This is because the eye of an insect consists of a number of small "holes"-facets. The eyes of insects are called compound. Tiny eye-facet is called ommatidia. Ommatidia has the form of a long narrow cone, the base of which is a lens having the form of hexagon. Hence the title compound eyes: facette translated from French means "face".
|Diagram of the structure of the compound eyes
1 - corneal facet; 2 - sitopladi apparatus;
3 - pigmented cells; 4 - optic cell;
5 - photosensitive element ommatidia;
6 - the processes of photoreceptor cells going in the optic ganglia;
7 - integument of head; 8 - eye capsule.
The beam of ommatidia is complex, round, eye of an insect.
Each of ommatidia has a very limited field of view: angle of ommatidia in the Central part of the eye is only about 1°, and the edges of the eye - to 3°. Ommatidia "sees" only one tiny area in front of the eyes of the subject on which he is targeted, i.e. where is the continuation of its axis. But as ommatidia closely adjacent to each other, and their axes in a round eye divergent beam, the entire complex eye covers the subject in General. Moreover, the image of the object obtained it in a mosaic that is composed of individual pieces.
The number of ommatidia in the eye in different insects is different. The worker ant in the eye just about 100 ommatidia, housefly is about 4000, the working bees - 5000, butterflies - 17 000, and dragonflies - up to 30 000! Thus, in the ant sight mediocre, while the great eyes of a dragonfly or two iridescent hemisphere provide the maximum field of view.
Due to the fact that the optical axis of ommatidial diverge at angles 1-6°, clarity insects are not very high: small parts they do not distinguish. In addition, most insects myopic: see the surrounding objects at a distance of only several meters. But to compound eyes are perfectly able to distinguish flashing (blinking) light with a frequency of up to 250-300 Hz (for a person limit frequency of about 50 Hz). The eyes of insects are able to detect the intensity of light (brightness), and in addition, they have a unique ability: able to define the plane of polarized light. This ability helps them to focus, when the sun is not visible in the sky*.
Insects are color blind, but not as we. For example, bees are not aware of the red color and does not distinguish it from the black, but perceive the invisible ultraviolet rays, which are located at the opposite end of the spectrum. Ultraviolet there are also some butterflies, ants and other insects. By the way, kapostu insect pollinators of our band to red due to the curious fact that among our wild flora no plants with red flowers.
*The light coming from the sun is not polarized, that is, its photons have random orientation. However, passing through the atmosphere, the light is polarized in the scattering by air molecules and the plane of polarization is always directed to the sun
By the way...
In addition to the compound eyes of insects have three simple eyes with a diameter of 0.03 to 0.5 mm, which are arranged in a triangle on the fronto-parietal surface of the head. These eyes are not adapted to distinguish between objects and the need for a very different purpose. They measure the average level of illumination that is in the processing of visual signals is used as a reference point ("zero-signal"). If you stick to these insect eyes, it retains the capacity for spatial orientation, but will be able to fly only when more bright light than usual. The reason for this is that the sealed eyes take over the "average" black box, and thus we set faceted eyes wider range of light and therefore reduces their sensitivity.