People often say, "rare is precious". It is true that observing uncommon species brings excitement to many nature lovers, but the beauty of nature is certainly not restricted to rarity! Our main species today--the Common Mormon, 𝘗𝘢𝘱𝘪𝘭𝘪𝘰 𝘱𝘰𝘭𝘺𝘵𝘦𝘴 Linnaeus, 1758 is widely distributed in Southeast Asia and is one of the most common species among the >250 butterfly species in Hong Kong. As a member of the swallowtail butterflies (Papilionidae family), the Common Mormon is a large butterfly with black wings and a characteristic series of white markings extending throughout the rear end of the wings. If you go hiking or take a walk in parks, the chances that you meet and enjoy their elegant flying styles is quite high!
Although they can be found everywhere, they are nothing close to a "simple" organism. You may be shocked when you know about their amazing survival strategies all along their different life stages! Butterflies are insects that have complete metamorphosis, which means their appearances can change completely when they grow up . When the Common Mormon is in its young larval stage, what is commonly referred as a caterpillar, they mimic something else to protect themselves from predators… Here, forget the elegant wings and beautiful black, white and delicate red colours as their mimicking model is bird poo ! The young larvae then have brown bodies with a white strip, looking just like bird droppings so their predators would not notice them or show any interest in eating them. As the caterpillars grow and enter the 5th instar, a developmental stage, their body colours become green. Additionally, they possess a Y-shaped red structure called osmeterium, which, when threatened, provides a bad smell to reinforce the aversion of a predator a bit too curious. For those of you familiar with Pokemon, this may sound familiar because that is exactly how the Pokémon Caterpie looks like with its design actually based on a swallowtail caterpillar!
After completing its larval stage, the caterpillars will complete their nymphosis through the pupal stage. The Common Mormon pupae, like many other butterfly species, will show pupal colour polymorphism. This means that different morphs exist with the colours of the pupae being either brown or green, mainly depending on whether they live on a bare brown twig or a twig with many green leaves. This is an example of camouflage, also known as cryptic colouration, where organisms use protective colours to help them blend into their surrounding environment.
Once adults, the Common Mormon still has a few tricks to enhance their survival. For long biologists have noticed that some harmless organisms mimic other well protected species; for instance some possessing powerful chemical deterring predators. In the Common Mormon, female-limited Batesian mimicry is encountered, where males only have one morph, and females have both a non-mimetic morph looking like the male, and a mimetic morph looking like the Common Rose 𝘗𝘢𝘤𝘩𝘭𝘪𝘰𝘱𝘵𝘢 𝘢𝘳𝘪𝘴𝘵𝘰𝘭𝘰𝘤𝘩𝘪𝘢𝘦, a poisonous species of butterflies .
The Common Mormon may be an ubiquitous butterfly, but they certainly play an important role in nature and have amazing ecologies. Insects may be small and easily neglected, but they are undoubtedly a part of nature's wonder! Next time when you visit the museum, take your chance to appreciate the specimens of Common Mormon and other amazing insect species!
Text: Winnie Lam
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