The Hub of Being (16-1-30) Insect Night Vision

 Insect Night Vision

Reliable vision in dim light depends on the efficient capture of photons. ~ Finnish biophysicist Anna Honkanen

The compound eyes of cockroaches are on the top of their little rounded heads, looking out with 2,000+ ommatidia. They can see all around. Cockroaches can even see when they shouldn’t be able to: when a photoreceptor in their eye only captures a single photon every 10 seconds.

The cockroach has extremely high night-vision capability. ~ Anna Honkanen

Cockroaches are not the only insect which can inexplicably see in the dark.

On a moonless night, light levels can by more than 100 million times dimmer than in bright daylight. Yet while we are nearly blind and quite helpless in the dark, moths are flying agilely between flowers. ~ Australian biophysicist Eric Warrant

Despite diminutive physical visual systems, nocturnal insects see so amazingly well in near darkness that they can distinguish colors, detect faint movements, learn visual landmarks for homing later, and avoid obstacles during their rapid flights. They can even orient themselves according to polarized moonlight.

For example, the nocturnal Central American sweat bee absorbs just 5 photons into its tiny eyes when light levels are at their lowest – a vanishingly small visual signal. And yet, in the dead of night, it can navigate the dense and tangled rainforest on a foraging trip and make it safely back to its nest. ~ Eric Warrant

The nocturnal elephant hawkmoth uses colour vision to discriminate coloured stimuli at intensities corresponding to dim starlight (0.0001 cd m–2). It can do this even if the illumination colour changes, thereby showing colour constancy – a property of true colour vision systems. In identical conditions, humans are completely colour-blind. ~ German zoologist Almut Kelber et al

The proffered physical hypothesis is that cockroaches and insect night flyers see 100 times better by summing photons “from different points in space and time.” According to this myth, disparate photonic summation somehow creates “super pixels” of imagery.

Spatial and temporal summation combine supralinearly to substantially increase contrast sensitivity and visual information rate. ~ Swedish neurobiologist Anna Lisa Stöckl et al

The physics of this are impossible, especially for creating a reliable visual image; but then consider the physical equipment these insects possess for vision processing, and even supralinear summation could not possibly provide the necessary visual acuity and color discrimination in such low light and at the speeds which many nocturnal bees and moths fly. While experiments have proven the visual abilities of nocturnal insects, accounting for these abilities by physical means alone can only be a science-fiction story.

Insect vision is precisely adapted to the light and movement conditions of their environment. ~ American biophysicist Simon Sponberg et al