Insects can see the world in much finer resolution than previously thought

September 5, 2017

Insects have much better vision and can see in far greater detail than previously thought, a new study from the University of Sheffield has revealed.

Scientists have long believed insects would not see fine images. This is because their compound eyes typically consist of thousands of tiny lens-capped 'eye-units', which together should capture a low-resolution pixelated image of the surrounding world.

In contrast, the human eye has a single lens, which slims and bulges as it focuses objects of interests on a retinal light-sensor (photoreceptor) array; the megapixel "camera chip" inside the eye. By actively changing the lens shape, or accommodating, an object can be kept in sharp focus, whether close or far away. As the lens in the human eye is quite large and the retinal photoreceptor array underneath it is densely-packed, the eye captures high-resolution images.

However, researchers from the University of Sheffield's Department of Biomedical Science with their Beijing, Cambridge and Lisbon collaborators have now discovered that insect compound eyes can also generate surprisingly high-resolution images, and that this has much to do with how the photoreceptor cells inside the compound eyes react to image motion.

Unlike in the human eye, the thousands of tiny lenses, which make the compound eye's characteristic net-like surface, do not move, or cannot accommodate. But the University of Sheffield researchers found that photoreceptor cells underneath the lenses, instead, move rapidly and automatically in and out of focus, as they sample an image of the world around them. This microscopic light-sensor "twitching" is so fast that we cannot see it with our naked eye. To record these movements inside intact insect eyes during light stimulation, the researcher had to build a bespoke microscope with a high-speed camera system.

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Vision assists ants to stabilise their head – until darkness falls

May 19, 2016

A study of Australian endemic nocturnal bull ants has found that they rely upon visual cues to stabilise their heads when navigating uneven ground.

The Macquarie University study, in collaboration with researchers from Australian National University, found that nocturnal bull ants stabilise their head using visual information. The ability to stabilise their head deteriorates as it gets dark. The study has taken the first steps towards identifying how insects acquire visual information in low light.

"We know that ants memorise visual scenes to navigate to specific places, such as their nest or a food source," said researcher Ajay Narendra.

"To compare a previously memorised view to the current one, they need to have a stable visual system. Imagine how distorted the view would appear when the head is rolled as they walk over a round twig or leaf!

"We wanted to see whether nocturnal ants employ compensatory head movements when their body rolls, and to what extent this ability is affected as light levels fall."

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