Global wanderer makes flying visit to coast
Swarms of dragonflies seen in coastal areas of Colombo last Sunday, suggest that a mass migration of these insects happened again.
Such an event in Sri Lanka was first reported by the Sunday Times in 2011 citing a researcher.
Dragonflies are migrating long distances, overseas researchers have found.
The sudden increase of dragonflies in some areas of Colombo suggest their annual mass migration happened last week.
Their sudden influx was mostly felt by those living in coastal areas. People near the Dehiwala Railway Station confirm they witnessed swarms of dragonflies on Sunday, October 20.
“It was around 8: 30 or 9: 00pm they started to come. They flew into our houses like those winged-termites [ meru in Sinhala],” said Chaminda Pushpakumara. Others shared similar experiences.
Hemal Pieris who lives on Kynsey Road in Borella found a dragonfly in his bathroom on an upper floor. “I haven’t seen a dragonfly in many years and was delighted. I gently coaxed it to fly away through the window,” Mr Peiris said.
Responding to a social media post by MigrantWatch who promotes observation of migratory species in Sri Lanka, many reported sightings.
Vishwamithra Kadurugamuwa witnessed them in Town Hall in Colombo 7.
“I Was actually telling my wife that it must be a dragonfly migration,” Mr Kadurugamuwa who had heard of the phenomena said.
Such a mass migration of dragonflies across Sri Lanka was first observed in 2011 by Nashath Hafi who is a member of the Field Ornithology Group of Sri Lanka that setup its MigrantWatch program. “I was waiting for the train at Moratuwa Railway Station in the morning watching some birds at the time and I observed a wave of dragonflies. Usually the dragonflies fly casually on a circular route, but they were moving southward. It was a spectacular scene,” Mr Hafi said.
He continued to observe the southbound dragonflies from Moratuwa to Kollupitiya.
Maldivian-based biologist Dr. Charles Anderson initially revealed this migration which he suggested could be happening across India to Maldives and all the way to Africa based on observations of mass gatherings in different areas.
According to Dr Anderson’s study, they fly 14,000 kilometres and it could be the world’s longest insect migration.
He calculated the dragonflies first appeared in the capital city of Maldives on October 21. And they were seen in Sri Lanka in 2011 on October 20. This year too the mass movement was seen on October 20. Dragonfly numbers peak in November and December, before the insects disappear once more. The insects stay for no more than a few days.
Indian observers also reported large swarms on beaches. A swarm was reported on the Mumbai coast on October 14 and different areas according to Sujith Chandran from Kerala.
According to Mr Chandran, the people in Kerala coastal areas know this phenomena happens with the onset of monsoon winds. “The locals believe the dragonflies emerge at a time when the sun enters Libra. In local language Libra is called ‘thula’ and dragonflies are called as ‘ thumbi’ — so locals named them ‘thula thumbi’”, he said
The migrating species is called the globe skimmer or globe wanderer scientifically known as Pantala flavescens. It is about 4.5cm long, and can have wingspans of 7.5cm.
The globe skimmer is considered to be the most widespread dragonfly on the planet with a good population on every continent except Antarctica although rare in Europe according to the literature.
Scientists at Rutgers UniversityNewark in the United States have studied the genes of the globe skimmer and found that specimens from different areas of the world have similar genetic profiles. In 2016, they published their findings in the journal PLOS ONE. They studied Pantala flavescens from US, Canada, Japan, Korea, India, South America and interpret the similarities as a result of long distant migration.
Earlier this week, on the coastal areas of Dehiwala, Wellawaththa and Bambalapitiya, swarms of dragonflies made up of 10 to 15 insects were seen, but by Friday, the numbers fell, observers report. This may mean they moved away from Sri Lanka to continue their journey toward Maldives, or spread inland.
There is much for researchers to find out.
The dragonfly migration could be yet another spectacular wildlife encounter Sri Lanka could be blessed to witness.