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The compound eyes of insects

H ace a couple of months I found a small mantid on the terrace of the house. I think it was a female ameers Spallanzani. took the opportunity to do various tests on a new flash, photographing it from different angles and with different backgrounds, while climbing up a pot of ivy not only unfazed by my presence. In fact, he accepted a fly approached him with pliers, I snatched it with a real craving and ate at a time almost before I could react, like a pet accustomed to human presence. But

that is the subject in which I bring to the blog, but fascinating compound eyes.

As can be seen in the next assembly, in their great big eyes see a black spot that seems to follow the look from where we look. It is true that finding, and fall into error because they tend to resemble the pupil of our eyes, when the vision process in insects is very different.

Actually the compound eyes of insects consist of an accumulation of pieces of a hexagonal tube, rather conical, called ommatidia, each of which captures an image portion having opposite. Is comparable to a lot of these pipes are stacked in the works. As we walk in front of them seeing the light of the fund, but is not that the light will go on, but we will see on the bottom of one or the other. In this case, the eye does not follow us to us, but we are seeing the bottom of each of these ommatidia.

In the diagram I made below shows that only the solid line arrow reaches the bottom of the eye where light-sensitive cells receive the image into the brain via the optic nerve. Thus each of the ommatidia receive images that are just in front of the brain forms a complete picture by adding all the partial images. In the scheme, point C corresponds with the cornea, which is a piece of skin as a lens, the initials CR with the lens, which collects the rays of light, the R to the rhabdom, the area where the photosensitive cells, and the optic nerve N . In insects

day the ommatidia are isolated from each other as said before pipes. But the night insects, to take advantage of low light, it it can pass from one side to another and the image formed is not only a sum, but a juxtaposition of partial images. In many other insects with large eyes and not so great, can be seen that point or dark stain. For example, the well-known in this blog, mountain cicadas. Perhaps the most stunning eyes of our fauna are those of dragonflies, which occupy almost 360 degrees of its surroundings. The spot "fundus" is broader due to the large number of ommatidia, because not only has a great eye surface, but also a high density of ommatidia per square millimeter, which provides a great visual acuity. Other highlights and changing colors of the eyes of insects are due to different internal areas of the ommatidia, which change as light strikes them.

The outer part covering the eyes, change with the rest of the skin in the successive changes of growth and metamorphosis. And within some species also have their own colors according to the design and color the rest of the animal, thereby Rosenberg at mimicry, as shown in this grasshopper and cricket blackness.

A curiosity: in the dead animals to become dehydrated, you lose the optical qualities of this whole complex of living lens, which can detect whether a picture of insect is a living or are we sneaking a dead body.

The following links you can find more information about the compound eye and the structure of the ommatidia , because as I have the habit, no attempt repeat content, but invited to observe.