Mediterranean Beetles Defy Norm as Rare Insects That Can See Red

It’s a common belief in science that insects can’t see the colour red — and until now, that belief went largely unchallenged. But a new study from an international team of scientists has revealed an astonishing exception. Two beetle species from the Mediterranean region possess a rare ability: they can actually perceive the colour red. This not only breaks with long-held assumptions about insect vision but also opens the door to rethinking how flowers and their pollinators have evolved together.

Most insects, including bees and flies, see the world through a limited colour palette. Their vision is typically tuned to ultraviolet (UV), blue, and green wavelengths of light. Red, a longer wavelength, is usually beyond their visual range. That’s why even when insects are found on red flowers, it’s not the red petals that draw them in. Flowers like poppies often reflect UV light patterns invisible to the human eye but highly visible to bees. So, insects may appear to favour red blooms, but in reality, they’re responding to something else entirely.

But in the case of Pygopleurus chrysonotus and Pygopleurus syriacus, two species of pollen-feeding beetles in the Glaphyridae family, the attraction to red isn’t a visual illusion. It’s real. These beetles, found in the eastern Mediterranean, are not just visiting red flowers like poppies, anemones, and buttercups—they are actually seeing them in red. And as the researchers discovered, they strongly prefer these bright red hues over others.

This discovery was led by Dr. Johannes Spaethe of the University of Würzburg in Germany, in collaboration with Dr. Elena Bencúrová and teams from the Universities of Ljubljana in Slovenia and Groningen in the Netherlands. Their findings were recently published in the Journal of Experimental Biology, and they mark the first clear experimental evidence of true red perception in beetles.

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To reach this conclusion, the researchers combined several investigative techniques. They used electrophysiological recordings to test how the beetles’ photoreceptors responded to different wavelengths of light. They also conducted field and behavioural experiments, exposing the beetles to coloured targets to see which they chose. The results were consistent: the beetles were not only capable of detecting red light but actively preferred red-coloured targets in natural settings.

What sets these beetles apart is the structure of their eyes. While most insects have three types of photoreceptors, these beetles have four. Their retinas can detect UV, blue, green — and deep red wavelengths. This additional receptor gives them access to a broader range of colours than nearly all other insect species.

According to Spaethe, the implications of this are much more than a visual quirk. These beetles may serve as a new model system for studying how insect vision evolves and how it interacts with ecological factors like flower colour. For decades, scientists believed that flowers evolved to suit the visual systems of their pollinators. Bees, for instance, tend to favour blue and violet flowers — and many flowers reflect UV light patterns that only bees can see.

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But if some pollinators, like these beetles, are developing enhanced vision to match the colours of the flowers they feed on, it suggests that evolution could be operating in both directions. Rather than flowers simply adapting to what pollinators can see, pollinators might also be evolving to better perceive the flowers in their environment.

This idea gains strength when examining the broader Glaphyridae family. The genera Eulasia, Glaphyrus, and Pygopleurus — all members of this group — show diverse preferences for flower colours. Some are drawn to red, others to violet, white, or yellow. This variation implies that the visual systems of these beetles are not fixed. Instead, their colour perception may be flexible and adaptive, shaped by the types of flowers available in their habitats.

The Mediterranean region, in particular, is rich in floral diversity. The abundance of flower colours, combined with the differing colour preferences of pollinating beetles, offers an ideal setting to study co-evolution — the mutual shaping of species through evolutionary pressures. It’s possible that the vibrant blooms of the region and the unique visual systems of beetles have influenced one another in a subtle ecological dance, played out over millions of years.

Spaethe and his team believe that further research into the visual systems of Glaphyrid beetles could offer valuable insights into how sensory systems evolve in response to ecological pressures. Their results suggest that beetle vision is not just about detecting food or mates — it might also be a case study in how perception itself can evolve under the influence of environmental richness.

So the next time you see a bright red flower buzzing with insect life, remember: not every visitor is colour-blind to red. Thanks to a few exceptional beetles, the world of insect vision just got a little more colourful — and a lot more interesting.