‘Twinkle twinkle little star. How I wonder what you are’. Have you ever looked upon the stars, and when the stars blink, poof, it is gone. There are flying blinking stars in the woods too, it is actually a way to survive, such as in the blue 𝘔𝘰𝘳𝘱𝘩𝘰 butterfly . Chosen as the species representing ‘butterfly’ in the emoji for apple smartphone users , the 𝘔𝘰𝘳𝘱𝘩𝘰 genus has a special place in people’s heart. Its distinguishably large, bright, iridescent and its blue wings are truly magnificent.
𝘔𝘰𝘳𝘱𝘩𝘰 𝘩𝘦𝘭𝘦𝘯𝘰𝘳 Cramer, 1782, also known as the common blue Morpho is found in the tropical habitats of Central and South America. Contrary to many other butterfly species feeding on flower nectar, adult morphos have a more original and diverse diet, feeding on rotten fruits, decomposing animals, tree sap, fungi and even mud, while its caterpillars feed on leaves.
Their blue colour and iridescent features are extremely rare in the natural environment since it can be a huge adaptive disadvantage, bringing lots of unwanted predatory attention within the environment. Then how such a costly colouration selected and maintained in nature ?
First, not all 𝘔𝘰𝘳𝘱𝘩𝘰 individuals are blue, or not during the entirety of their life. For instance, the eggs of 𝘔. 𝘩𝘦𝘭𝘦𝘯𝘰𝘳 are pale green and are shaped like dew drop; while the caterpillars are red-brown with bright green spots. The adult males are the ones displaying the pretty flashy blue, while the females are mostly brown with smaller and more faded blue marks. In addition, the dorsal side of the wings in both male and female are brown with a number of yellow spots, meaning that when the wings are closed, the butterfly goes into a stealthy mode. Something worth noting is the presence of gynandromorphs, or if you prefer individuals carrying both male and female features. Gynandromorphs are found in many groups of insects, and in the case of the Morpho this results in individuals having a ‘male’ blue wing on one side and a ‘female’ brown wing on the other.
Blue is a rare colour in nature because this colour usually requires a complex blue pigment which is unstable and costs more energy to produce than other pigments. This is why the blue on the wings of morphos is actually not a ‘colour’, but an iridescent form of structural colouration. The wings of butterflies are covered with tiny scales, and the iridescent blue colour is caused by light reflecting on the microscopic scales that are covering the wings. (If you want to know more about the wings of Lepidoptera (butterflies and moths) remember to check this older post out > https://bit.ly/3PQnyEz) When you look at it from different angles, the colour changes ranging from blue to violet, or even to green and orange.
The iridescent blue is used as a visual signal for both “friends” (intraspecific = same species) and potential enemies (interspecific = other species). At the intraspecific level, it has a function for reproduction and is an example of sexual dimorphism, meaning males and females look different. Here, the male is more attractive than the female and the bright blue colours are used to attract the opposite sex and influence their mating choice while competing against other males . It is also used as a bright warning to other 𝘔𝘰𝘳𝘱𝘩𝘰 males in the area that they entered into the territory of another male - with 𝘔𝘰𝘳𝘱𝘩𝘰 being very territorial. At the interspecific level (with other species), the intense, iridescent and glossy blue can cause sensorial confusion to the predators; just like an intense spotlight right in their face which may stun them. When these butterflies flap their wings and fly, they blink like stars in the sky! The constant changing of the glossy top side and the darker bottom side creates an illusion for the predators, causing the butterflies to look like they’re disappearing and reappearing, making them harder to localize precisely and thus catch.
When they rest, they fold their wings like a closed book. The brown colour on the back allows males to also be camouflaged in the woods and avoid attraction while sleeping. Just trying to have a good night’s sleep here don’t we all ? There are also brown circles on both the bottom wings of the male and female 𝘔𝘰𝘳𝘱𝘩𝘰s called eyespots. Those imitate eyes to warn predators and preventing these to attack their most vulnerable and vital parts of the body, this adaptation is called eyespots automimicry.
If the colours of butterflies have inspired artists for a long time, the iridescence of Morpho also had a more applied function, as it inspired the making of the iridescent strip on dollar bills . There is always something to learn from nature, thus the importance of protecting it. While one may be tempted to capture or purchase one of these beautiful butterflies to display them at home, such behaviour is partially responsible for the endangered status of this species. Thus refrain from purchasing butterflies or other decorative/pet species to give a chance to future generations to appreciate these furtive stars in their natural environment. And if you want to appreciate their beauty and diversity, visit instead natural history collections such as the HKBM!
Text : Nadine Ma
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