Bhutan’s national butterfly, Ludlow’s Bhutan Glory (Bhutanitis ludlowi), has its life cycle recorded for the first time in its endemic area of Bumdeling in Trashiyangtse.
Senior forestry officer with the Bumdeling Wildlife Sanctuary (BWS) in Trashiyangtse, Tshering Dendup, released an adult Ludlow’s Bhutan Glory into nature after recording the complete life cycle of the butterfly on August 21, 2017.
The researcher introduced the freshly laid eggs collected from its natural habitat in Rigsum Goenpa into an ex-situ environment, a greenhouse constructed at BWS.
He then created a thriving environment artificially through the establishment of Aristolochia (its novel host plant) nursery inside a greenhouse.
Usually, the butterflies in the valley are distributed sporadically at an altitude range of 2,200 to 2,500 metres above sea level (masl). The eggs were, however, incubated in the ex-situ environment that was created at an elevation of 1,752masl.
Over the next 367 days, Tshering Dendup closely observed the metamorphosis of the national butterfly recording each change in the physical appearance of the species.
He said that the mean total duration from egg-laying to hatching was 18 days of incubation in an ex-situ environment inside the greenhouse. “Soon after the emergence from the egg, the larva consumes its eggshell before it spreads to feed on young tender leaves of the host plant.”
He said the larva passes through eight larval instar stages and a pupal stage before emerging as an adult butterfly over an incredible period of 367 days. “Probably, this is one of the longest life cycle period for a butterfly.”
The stages between molts are known as instars. A young caterpillar that first hatches from its egg is referred to as first instar caterpillar and the caterpillar’s first molt is referred to as second instar.
The life cycle completes in 367 days with egg hatching (14-18 days), larva (five months and eight days) and pupa (six months and seven days). After 188 days, the adult butterfly emerged from the chrysalis.
Tshering Dendup said that it was an emotional day when he finally went to release the adult butterfly back into its natural habitat in Rigsum Goenpa. “For more than a year, I have been closely nurturing and watching it grow through instars. You develop a bond with it and when you finally let an adult flutter off into nature, it is an emotional moment.”
Brightly coloured, the adult male has a wingspan of about 58.2mm to 60.3mm. The female is usually larger with a wingspan of about 61.02mm to 63.0mm.
Ludlow’s Bhutan Glory was officially endorsed as the national butterfly in 2012 during the 123rd sitting of the Cabinet.
Listed vulnerable under the International Union for Conservation of Nature (IUCN), not much was known about the butterfly species until now.
The butterfly was first discovered by plant hunters, Frank Ludlow and George Sheriff at Tobrang, upper parts of Trashiyangtse valley in 1933-34.
Endemic to Bumdeling valley in Bhutan, Ludlow’s Bhutan Glory was rediscovered after 75 years in 2009 by a Bhutanese forester, Karma Wangdi.
Tshering Dendup said that except for the limited information of the species description, none of the reports described the complete details of its life cycle stages.
He said that a joint research team of Bhutanese from the agriculture and forest ministry and Japanese lepiodpterists from Butterfly Society of Japan made the only reference to the life cycle of the early stages of the species.
The team compared Bhutanitis ludlowi’s morphological characteristics with Bhutanitis lidderdalii Atkinson (Bhutan Glory) till the second instar of its early immature larval stage and adults.
“Apart from this study, no complete study on its life cycle was conducted,” Tshering Dendup said. “The present study, for the first time of such kind in Bhutan and in the world, demystifies and elucidates the complete life cycle of Bhutanitis ludlowi on its novel larval host plant, Aristochiaceae.”
Along with the life cycle of the butterfly, the researcher also observed the defence mechanism of the species from its natural predators and details about its host plant.
Tshering Dendup said that although there has been no research conducted on the number of the butterfly in the area, Ludlow’s Bhutan Glory had high mortality rate and a majority of them were not able to turn into adults from a few hundred eggs.
“We had made attempts for studies in its natural habitat in the past but we could not succeed since the study locations were far away from the head office,” he said. “Lack of awareness among the local communities attributed to the failure as the research sites were found destroyed and observation plot trees cut down along with the larvae and host plants.”
He said that given the vulnerable status of the butterfly, awareness programme and support groups would be formed in the community with support from the BWS in the future. “Enrichment plantation of the host plants would also be carried out.”
Younten Tshedup | Bumdeling