The Golden Birdwing, or Troides aeacus, is a sizable butterfly that's part of the swallowtail family, Papilionidae. These are found throughout East, South, and Southeast Asia tropical forests and reside in various regions, which include Northern India, Nepal, Burma, China, Thailand, Laos, Vietnam, Cambodia, peninsular Malaysia, and Indonesia, usually in the range of 300 to 2000 meter above the sea level. In most areas, the International Union for Conservation of Nature (IUCN) Red List categorizes them as Least Concern species. Recently dubbed India's largest butterfly with a wingspan of 194mm, the Golden Birdwing dethroned the former record holder that had been documented by British army officer Brigadier Evans in 1932.
As a large species, they tend to favor open or sparse areas within the forest, which allows for ample room during flight. They can fly very high and are seen flying above the forest canopy. They also fly close to the ground too for nectarine. These striking butterflies can often be spotted near a flower's corolla where they blend in with fluffy pollen-covered hairs. This helps them with pollination. They feed on plants without causing significant disturbance. However, if you notice their numbers growing rapidly, it's essential to treat it with some gravity.
Both the caterpillars and adults of the Golden Birdwing species are generally toxic. They primarily feast on plants from the Aristolochia genus which contain aristolochic acid—a substance notoriously carcinogenic and nephrotoxic. This toxin can accumulate in adult worms and make them poisonous. However, humans shouldn't worry too much; these toxins mainly affect their prey and predators. Though ingesting such toxins could still harm humans on some level.
Characteristics of the Male The Golden Birdwing Butterfly
The forewings of male specimens are black in color with veins bordered by whitish color, while their hindwings boast a vibrant yellow hue.
On the upper side of the forewing, there are prominent streaks in the adnervular, which is the area near or along the veins. Similarly, on the upper side of the hindwing, cone-shaped black markings can be found in specific regions, surrounded by a shadowy area sprinkled with tiny blackish scales.
Notably, the area near or along the veins on the upperside of the forewing features prominent streaks. The black coloration along the front edge of the wing, referred to as the coastal margin, is somewhat narrow and doesn't quite stretch to the tip but stops at a certain vein. Interestingly, the underside of the wings closely resembles their upperside. The abdomen showcases two rows of black spots, and the head, thorax, and abdomen are predominantly black in color.
Characteristics of the Female The Golden Birdwing Butterfly
The females are larger than the males and have dark-brown or black wings. The head, thorax, and abdomen of this butterfly are mainly black, with small red patches on the thorax and a yellow underside of the abdomen.
On the top side of the forewing, similar to the male, there are incredibly wide and noticeable streaks in the adnervular area. The upper side of the hindwing features a black color near its base, while the middle parts have a yellow hue in the front and a soft white from the back. In the rear half of the central region of the wing, you can spot scattered black scales. Interestingly, some of these black scales are interrupted by a small yellow spot on the inner side and another one on the outer side.
Life Cycle of The Golden Birdwing Butterfly
The Golden Birdwing butterfly, known scientifically as Troides aeacus, experiences four incredible life stages just like any other butterfly. These include the egg, caterpillar, chrysalis, and finally, the adult butterfly stage.
When a female Golden Birdwing finds her mate and becomes fertile, she starts laying her eggs, carefully tucking them under leaves or on nearby plants for protection. In less than a week's time, a little caterpillar emerges and often devours its eggshell as a sneaky move to hide its existence.
As the caterpillar grows, it munches on the leaves of its host plant. There are five distinct growth sub-stages that these caterpillars go through called instars. During this journey, they shed their skin to accommodate their growing bodies. One of the unique traits of Troides aeacus caterpillars is their size and striking appearance—they're quite large and wear a lovely pale brown color accompanied by long thorny protrusions with pink tips. To ward off predators, they release a peculiar scent from an organ in their head. They mainly feast on plants from the Aristolochiaceae family.
Once it's time for a major change, the caterpillar picks a comfy spot to undergo its magical transformation. It hangs itself upside down and turns into a chrysalis within an hour or so. It's during this stage that the caterpillar's body breaks down and reforms into a gorgeous butterfly.
After about two weeks in the pupa stage, the chrysalis cracks open, and out comes the adult Golden Birdwing. Hanging upside down from its former shell, the butterfly carefully dries its wings and inflates them fully with fluid. With just 2-3 weeks left to live in this final form, it's now time for them to find a mate and start the cycle all over again.
Discovering The Golden Birdwing Butterfly in Nepal
These beautiful butterflies mainly reside in the lowland and midland forests of central Nepal, which includes Kathmandu Valley, Makwanpur, and Nuwakot among others. Occasionally, they've been spotted at a staggering 3,000 meters above sea level! Your best chance to catch a glimpse of them is during their active season—from April to September.
Unfortunately, though the Golden Birdwing butterfly (Troides aeacus) might not be deemed endangered, but its numbers are sadly dropping in Nepal. Recent studies conducted across central Nepal reveal that threats to its habitat have led to this decrease. Factors like the loss of its natural environment, a lack of nourishing plants for the adults and their young, an increase in tourism activity, road construction, forest fires, and even small landslides have caused some hiccups in the butterfly population.
Conclusion
Taking into account all the information we've gathered, it's clear that the Golden Birdwing (Troides aeacus) is an impressive, large butterfly. It has recently gained recognition as the largest butterfly discovered in India, boasting a wingspan of 194mm. Currently, it's not classified as endangered. However, given the declining population in Nepal, this might hold true for other areas as well. Now is the time to turn our attention towards preserving these magnificent creatures before they face the risk of endangerment.