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An interesting butterfly rescue
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Phil Morland
United Kingdom
Oct 09, 2021
@Jesuslove(Hannah) Hi Hannah. First, regarding the colouration of male Apatura iris' wings. The blue or purple colours we see are not true colour pigments at all. They are iridescent. As the sun's rays hit the surface of the wings they are refracted (bent) by the shape of the scales on the wings. Many species of lepidopterans have this (see Madagascan Sunset Moth for another example). Depending on the angle the wing is viewed from, a male Apatura iris can appear from dark blue to deep purple. The actual colour pigment of a male's wings is brown, like the female's, but females never appear blue or purple because they are not iridescent. When you see a photograph where only a proportion of the butterfly's wings seem purple it is down to the angle the photographer was in relation to the butterfly's wings. If the butterfly moves its wings or the observer moves his or her position, the amount of apparent blue or purple will change. Males have evolved iridescent wings as an aid to attracting a mate. Diet and distribution doesn't affect how the light is refracted, so doesn't change how much purple or blue is shown. General condition of the butterfly does though. As a butterfly grows older it loses more and more scales from it's wings - so less light is refracted. You can learn more about iridescence here. Females are larger than males as females need larger abdomens and wings in order to carry their eggs. Often the number of eggs carried can be in the hundreds. The best place to find Apatura iris in the UK is in the southern counties of Hampshire, Surrey and Sussex, although they do appear to be moving slowly northward, possibly because of climate change, as they seek cooler climes and denser forests. They are a difficult butterfly to observe as they spend most of the time high up in the canopy and rarely come down to the ground. In the UK they are quite sparse, there are more concentrated populations in Central Europe. I have seen them in the New Forest (a bit of a misnomer as it is an ancient forest) but only from afar in the tree tops. Thanks for your questions Hannah. Keep them coming, it's how we all learn.
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Phil Morland

United Kingdom
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