If you have been to Samphire Hoe recently, or have read our recent trip report, you will know that Samphire Hoe is a great place to find rose chafer beetles. Rose chafers are quite big beetles, very friendly, and easy to watch as they feed on the flower heads of wild carrot, large knapweed and other such plants. Although the beetles are basically green, they are very shiny and iridescent. They are living jewels!
But their colours are literally only skin deep. Rose chafers are a really good example of “structural colouration” where the colours are produced by the reflection and refraction of light from the outermost layers of the chitin. This is further enhanced by micro-sculpture on the surface. Sally’s photograph shows this brilliantly – with lines and punctures of varying depth. The different wavelengths of light are affected so that, as the beetle changes its position, its colour changes. (Believe it or not I used to teach physics and thought I could explain this – but now I just can’t get my head round it!). Try this if you want to know more.
But I still find structural colours fascinating. This photograph is of a tiny parasitic wasp (probably Ormyrus nitidulus). Its larva attacks many of the insects that produce galls on oak trees. You would need about 30 of these to cover the back of one rose chafer! But just look at the micro-sculpture on this species. It is basically a deep blue colour but as it moves it varies from green to purple with gold tints. This group of wasps has been called “the jewels of the grassland”. But what are the colours for? How did they evolve? What do the insects themselves actually see?
The warden at Samphire Hoe told us that 71 rose chafers had been counted the day before our visit. This immediately reminded me of the marvelous character of the “Rose Beetle Man” in Gerald Durrells’ “My Family and Other Animals”. The young Gerry meets the Rose beetle man walking along a hot dusty road in Corfu. Amongst other things, he was carrying lengths of cotton thread to each of which was tied a rose chafer beetle. They were buzzing and swirling around his hat, desperate to escape, and “glittering golden green in the sun”. Later we learn that Gerry buys all of them.
“..when [the rose beetle man] had left, [we] let them all go in the garden. For days the villa was full of rose-beetles, crawling on the beds, lurking in the bathroom, banging against the lights at night, and falling like emeralds into our laps.” Gerald Durrell – My Family and Other Animals.
I’m all for that. Nature is amazing, let’s keep it that way.
Thanks to Sally for the photographs