Dragon Ocelli

Most flying insects have three simple eyes arranged in a triangle configuration, in addition to the two large compound eyes that we are all aware of. These three extra eyes, called ocellus (singular) or ocelli (plural), are single lens' (simple), as can often be seen when using flash, when the retina lights up as the light reflects back to the camera lens.

Although the eye consists of a lens and a retina of light sensitive cells, it cannot form an image as we know it, because the light entering the lens is focused some distance behind the retina. The three eyes are however, sensitive to variations in light, low levels of light and have a rapid response.

Although it has not been proven what the exact function of the three ocelli is for flying insects, it is generally accepted that they function as a flight stabilizer. Triangulated information integrated to provide a sense of horizon. Although a compound eye would probably be capable of providing this information, the reaction speed of the ocellus would be more suited to the purpose.

Some documents suggest that the ocelli are for determining daylight timing, like an internal clock. I'm not buying this idea though. Such a feature would not require three ocelli nor would the high speed of the ocelli be required. Maybe as a secondary function, yes.

Many non-flying insects also have ocelli, sometimes two or even one ocellus. Sensitive light measurement being useful to a ground insect, but three ocelli not being necessary.

It occurred to me that the three ocelli arrangement could be used as a triangulation location function, enabling the insect to navigate, but I never found mention of this possibility in the documents that I read. This does not mean that it is not so, science is a long way from knowing everything.

A bit of a tedious read today, so if you got to the end then well done. Any opinions will be received with interest.

Dave