Get fluttering: it's the day for rare butterfliesLocal | Lauren Lau 21 Jun 2019
A green group says today will be the best opportunity to get a glimpse of four rarely seen butterfly species.
Analysis by Green Power shows that this summer solstice will be the prime period to observe the common rose, swallowtail, golden birdwing and common birdwing.
The first three species are categorized as "uncommon," while the fourth has been classified as "rare."
Butterflies are classified based on five categories that range from very common to very rare.
Hong Kong is home to 260 different species of butterflies.
Since 2005, Green Power has been collecting data and investigating the correlation of solar terms and butterfly observation.
The golden birdwing and the common birdwing both belong to the Genus Troides of the Papilionidae family. They are the only two kinds of insects in Hong Kong that are legally protected.
The four types of butterflies are not commonly seen in the city due to their diet.
During the larvae stage, they only consume one to two types of rare plants and therefore they don't breed in large numbers.
Their pretty wings also attract hunters as the common birdwing and golden birdwing have contrasting colors of black and yellow.
Many hunters treat them as prestigious pieces for their collections, causing them to be targeted and killed.
Matthew Sin Ka-wah, the group's senior environmental affairs manager, said temperatures must reach a certain level for butterflies, especially those with bigger bodies, to be active.
"Therefore, when the weather is warmer, especially during the summer solstice, these butterflies will appear more frequently," Sin said.
There has been an increase in swallowtails, but the number of the other three types of butterflies fluctuated between 2013 and 2016.
The common rose used to be a very common species during the 1960s, but its numbers suddenly declined between 1975 and 1984.
Even though the government has been helping in providing the dietary plants of its larvae, the common rose hasn't been able to return in vast numbers.
"The reason behind it is yet to be known. More studies and investigation on it is needed to find a fitting conservation scheme for them," Sin said.