Butterfly ‧ Hill Topping

Some butterflies have special habitat preferences. We can learn about their preferences by comparing the distributions of different species of butterflies. Some species, such as Agehana maraho of Taiwan, favour higher altitudes. To observe them, one must climb to over 2,500 metres, and have some luck. These high-altitude species are known as "montane butterflies". Although there are numerous mountain ranges in Hong Kong, their altitudes are not as high as those of Taiwan and China. The highest peak of Hong Kong — Tai Mo Shan — is a mere 957 metres in altitude. So, there is no true montane butterfly in Hong Kong. Yet, hill-topping species can still be found.

Most hill-topping butterflies fly towards the highlands by following the topography in the early morning. They gather on the peaks and ridges. Individuals of the same species will ascend the peak around the same time, hence increasing their chances of meeting the opposite sex, and saving their time and energy. After arriving at the peak, the males will soar around and occupy the best sites to wait for the females. The competition between the males is ferocious, and they will often chase after each other. The females, on the other hand, will choose their ideal partners; after mating, they fly to lower ground to lay their eggs.

Hill-topping behaviour is affected by a variety of factors, and it may not be easy to encounter these butterflies. Butterflies are more active in sunlight, so most ascend the peaks on sunny days. Timing is also important. Reproduction periods vary between species. Hill-topping, the precursor to reproduction, is at different times of the year for different butterflies. Geographical location is another factor. Peaks that are surrounded by lowlands, such as Kwun Yam Shan, Kai Shan and the Peak, are often the only choice for the butterflies in the region. Therefore, there are higher chances of meeting groups of courting butterflies on these peaks.

Butterflies which may have hill-topping behaviour
Tawny Mime (Chilasa agestor), Indian Fritillary (Argyreus hyperbius), Painted Lady (Vanessa cardui), Constable (Dichorragia nesimachus), Courtesan (Euripus nyctelius), Danaid Eggfly (Hypolimnas misippus), Peacock Royal (Tajuria cippus), Silver Streak Blue (Iraota timoleon), Orange Punch (Dodona egeon)

Courtesan (Euripus nyctelius)

Danaid Eggfly (Hypolimnas misippus)

Silver Streak Blue (Iraota timoleon)