animal eyes
Bees see ultraviolet maps on flowers. Ants steer by the polarised sky. Bats paint the dark with echoes. Step into one 3D meadow and swap eyes with nine animals. Every view is built from published research on their photoreceptors.
Fly close to the flowers. The plain yellow ones have a hidden ultraviolet bullseye that only bees can see!
Apis mellifera
Bees see UV patterns on petals (“nectar guides”) that point the way to the food.
No red receptor: a red poppy looks dark or UV-coloured to a bee.
Special cells at the top of the eye read the sky’s polarisation pattern like a compass.
Bees judge flying speed and distance from how fast the world streams past.
Each bee eye is made of about 5,500 tiny tubes called ommatidia. Each one has its own lens and looks in a slightly different direction, so the bee’s picture is a mosaic, like a picture made of hexagonal tiles.
A 2025 study tracked bees learning patterns and built a brain model of their visual system. Bees don’t take still snapshots. They scan scenes with flight movements, and neurons in the lobula learn to use that motion to recognise shapes.
MaBouDi et al. (2025) A neuromorphic model of active vision… eLife 14:e89929 ↗Light enters an ommatidium (or a spider’s retina) and travels into the rhabdomere: a brush of up to tens of thousands of tiny tubes called microvilli.
Go deeper: A fly photoreceptor has about 30,000 microvilli. Each one is a separate light-detecting unit.
Light is made of photons. A photon has a wavelength (its colour), a direction of vibration (its polarisation), and it arrives at some rate (brightness and flicker). Every eye in this viewer measures some of these properties and ignores others.
Shorter wavelengths carry more energy per photon: E = hc / λ. A 350 nm UV photon packs about 60% more energy than a 560 nm green one. Each photoreceptor's pigment absorbs best at one wavelength (its λmax) and less on either side. An eye compares cells with different λmax to see colour.
Sunlight scattered by the air vibrates mostly in one direction. That direction makes a huge pattern of rings around the sun. Insect photoreceptors with neatly aligned microvilli can read it, even on cloudy patches of sky, and use it as a compass.
In moonlight each cell catches only a few photons, and the randomness of their arrival makes the picture grainy (“photon noise”). Big pupils, mirror layers (tapeta) and rod cells help an eye catch more of them.
How fast a photoreceptor recovers sets its flicker-fusion frequency: the flicker rate where a blinking light starts to look steady. It is about 60 Hz for us, about 200 Hz for a bee, and at least 129 Hz for a peregrine falcon.
Animals with backbones and animals like insects and spiders evolved two different photoreceptor designs. Both start with the same trick: a protein called opsin holding a light-catching molecule, retinal. After that, the two designs work differently.
| 🧒🐕🐈🦅🦇 Ciliary (rods & cones) | 🐝🪰🐜🕷️ Rhabdomeric (microvilli) | |
|---|---|---|
| Where the pigment sits | Stacked membrane discs in the outer segment | Tens of thousands of finger-like microvilli (a rhabdomere) |
| G-protein | Transducin (Gt) | Gq |
| Enzyme | PDE6 destroys the messenger cGMP | PLCβ cuts the membrane lipid PIP₂ |
| Ion channels | CNG channels close | TRP / TRPL channels open |
| Voltage change | Hyperpolarises (more negative) | Depolarises (more positive) |
| Used pigment | Retinal is released and must be recycled by neighbouring cells | Bistable: another photon can switch metarhodopsin back |
| Polarisation sensitivity | Very weak (discs are randomly oriented) | Strong when microvilli are aligned |
| Speed | Slower; rods integrate light for longer | Very fast, which suits flying insects |
Step through each design, plus a bat’s hearing, in the animated “From photon to signal” panel above. It switches automatically when you pick an animal.
| Animal | Photoreceptor peaks (λmax) | Eye type | Sharpness | Field of view | Flicker limit | Special sense |
|---|---|---|---|---|---|---|
| 🧒 Human | 420534564rod 498 | camera | 60 cyc/° | ≈200° | 60 Hz | Sharp, three-colour daytime vision |
| 🐕 Dog | 429555rod 506 | camera | 12 cyc/° | ≈250° | 75 Hz | Night vision and a wide view |
| 🐈 Cat | 450556rod 501 | camera | 7 cyc/° | ≈200° | 55 Hz | Sees in about 1/6 of the light we need |
| 🐝 Honeybee | 344436556 | compound | 1.8° per facet | ≈320° | 200 Hz | Sees UV and the sky’s polarisation compass |
| 🪰 Dragonfly | 330410460525630 | compound | 1.1° per facet | ≈355° | 250 Hz | Nearly 360° view and up to 30 light-sensing genes |
| 🐜 Ant | 350510 | compound | 3.5° per facet | ≈300° | not well measured | A sky compass and a memory of the skyline |
| 🕷️ Jumping spider | 360530 | 8 eyes (camera-type) | 12 cyc/° | ≈360° | not well measured | Telephoto eyes plus motion-detecting side eyes |
| 🦅 Eagle & falcon | 405450505565rod 503 | camera | 140 cyc/° | ≈250° | 129 Hz | About twice as sharp as us, with two foveae per eye |
| 🦇 Bat | 360555rod 500 | camera | 1 cyc/° | ≈240° | not well measured | Builds a 3-D picture from echoes |
Sharpness for camera eyes is in cycles per degree (human ≈ 60). For compound eyes we give the angle between neighbouring facets, because each facet is roughly one “pixel”. Peaks are typical values for one well-studied species in each group.
Want to go further than this viewer? These are the books and papers scientists themselves recommend. Start at the top, and work down as you get more curious.
Great for curious kids, parents and teachers. No equations needed.
Reviews summarise many studies at once. They are the fastest way into the research.
The ideas behind this simulator, and where its simplifications come from.
For older students and teachers who want to analyse real photos and spectra.