Large, dark-coloured moths some nearly the size of a human hand have been spotted all over Singapore in recent weeks, drawing curious onlookers from Raffles Place to Woodlands.
Since the middle of last month, nearly 800 sightings of the Lyssa zampa, or tropical swallowtail moth, have been reported online, said National University of Singapore ecologist N. Sivasothi, who is recording sightings on the NUS Habitat News website.
They have been seen at many places, including office buildings, HDB corridors, schools and parks.
The moth is present here year-round, but is more commonly seen between May and August. Ecologists say the last major flurry of sightings was in 2005, with minor spikes every year or so since.
After well-known blogger Mr Brown tweeted about Mr Sivasothi's effort on Monday, page views at the NUS Habitat News website yesterday shot up to 18,000, from 200 to 300.
Insurance specialist Tovia Kwan, 38, saw around 100 fluttering above the Jalan Besar stadium at the LionsXII football match on Tuesday night.
"Some of them seemed to be dive-bombing the pitch," she said. "Hopefully, it didn't put off the Lions players, as they went on to lose the match."
The native moth has also taken a liking to the financial district.
"You can pretty much see one or two on every pillar and wall here. There must be hundreds or thousands," copywriter Jasmine Osada, 29, said yesterday. She added that the moths first started appearing a week ago, and have been giving office workers a fright by flying into lobbies and lifts.
The sighting numbers are probably under-reported, said butterfly expert Khew Sin Khoon, an honorary research affiliate at the Lee Kong Chian Natural History Museum. The moth's population is unknown.
The nocturnal moth lives in forests here and elsewhere in the region. The span of its dramatic, sculpted wings can reach 16cm, making it the second-largest moth here after the Atlas moth.
Its caterpillars feed on the leaves of a species of rubber tree, though "not much else appears to be known", said Mr Sivasothi.
It is attracted by lights in urban areas, he added, while during the day, it rests in cool, shady places. "These (sightings) are part of natural cycles we should look forward to and celebrate in Singapore," said Mr Sivasothi. He emphasised that the moths are harmless.
Mr Khew believes that one possible reason why there are so many moths around is that the numbers peak with the end of the bird migration season from September to March. Fewer predators could mean more chances for them to venture out, he said.
He urged people to look out for the moths now, as their lifespan is about two weeks.
Additional reporting by Richard Newlove