Hover Flies, such as the this one above, look at the world in quite a different way than humans do. The structure and function of a flies eye are completely different from ours, and so they see shapes, motion and color differently. Flies are also able to see light in a way humans cannot.
Structure of a Compound Eye
Compound eyes are made up of thousands of individual visual receptors, called ommatidia. Each ommatidium is a functioning eye in itself, and thousands of them together create a broad field of vision for the fly. Each ommatidium is a long, thin structure, with the lens on the outer surface of the eye, tapering to a nerve at the eye’s base. When the ommatidium receives light, it is filtered through the lens, then a crystalline cone structure, pigment cells and visual cells. Every ommatidium has its own nerve fiber connecting to the optic nerve, which relays information to the flies brain.
Flies Can’t Focus
A human’s eye is attached to muscles that allow it to move, expanding the field of vision and making it possible for the eye to gather more information about its surroundings. Instead of moving their eyes, flies receive information from several different points simultaneously. A flies eyes are immobile, but because of their spherical shape and protrusion from the flies head they give the fly an almost 360-degree view of the world. In a human eye, the pupil controls how much light comes into it, which is focused by the lens onto the retina. The retina then relays information to the brain via the optic nerve. Because fly eyes have no pupils they cannot control how much light enters the eye. With no control over how much light passes through the lens, the fly cannot focus the image it sees. Flies are also short-sighted — a visible range of a few yards is considered good for an insect.
The Mosaic Effect
The best analogy to describe a flies vision is to compare it to a mosaic — thousands of tiny images convalesce, and together represent one visual image. Each one of these pictures represents information from the fly’s individual ommatidium. The effect is much like how we see stippling or newspaper print — up close the image is a lot of tiny dots, but take a step back and it’s a complete image. The more ommatidia a compound eye contains, the clearer the image it creates.
There’s a reason why flies are especially jumpy creatures that take off at the slightest flinch. A flies vision is nowhere near as clear or effective as a human’s, but it’s especially good at picking up form and movement. As an object moves across the fly’s field of view the ommatidia fire and stop firing. This is called a flicker effect. It’s similar to how a scrolling marquis works — with lights turning on and off to give the illusion of motion. Because a fly can easily see motion and form, but not necessarily what the large moving object is, they are quick to flee, even if the moving object is harmless.
Flies have limited color vision. Each color has its own wave frequency, but flies have only two kinds of color receptor cells. This means they have trouble distinguishing between colors, for instance discerning between yellow and white. Insects cannot see the color red, which is the lowest color frequency humans can see. However, houseflies have the ability to see polarized light, but humans cannot differentiate between polarized and unpolarized light. Polarized light is light in which the waves travel only in one plane.
To be an Insect ?
Very often when I am out in our local woodlands with a Macro lens, I like to get in close and find all kinds of Insects to photograph. Its like a completely different universe down at this level, I find that I also end-up studying what these little creatures are doing in-order to keep existing day to day.
I often wonder how they see the same world that we share with them, what perspective they have on life without our daily activities and life styles.
Life without News and Media communication, life without TV or Radio and the latest phone, Life without Cars or Vans and Motorways – No Banks or need for Money with Tax to pay.
I wonder if we could even for one moment, a single day, begin to understand just how much of life in our world exists without all the things that we surround ourselves with, thinking that we actually need then in order to exist?
I also wonder when capturing nature with a camera, if its possible at all to capture these questions, to get across the true existence of a bee or a hover-fly, not only showing the outwards wonder of these insects but capturing the life that they are actually living ?
At this time of year our local woodlands are full of wildlife with the insects at the height of their activities.
I was lucky enough to capture this Predatory Sawfly, yesterday evening, just while there was enough sun-light left to help get a bright image 🙂
Sawfly is the common name for insects belonging to suborder Symphyta of the order Hymenoptera. Sawflies are distinguishable from most other hymenopterans by the broad connection between the abdomen and the thorax, and by their caterpillar-like larvae. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plants where they lay their eggs. Large populations of certain sawfly species can cause substantial economic damage to forests and cultivated plants.
A few days ago while out walking , I took a rest and sat-down for a while in the corner of a field.
I noticed these Dandelions and that they were providing a feast for all kinds of insects, so I took lots of images a few of which I post here.
I love this time of year as life is everywhere, so why not just take a moment or two and take a look at all that surround you.
In September all the insects in the hedgerow seem to come to life, they feed frantically on the remaining flowers and fruit before the Autumn takes hold.