A valley in southwest China's Yunnan Province is seeing the largest butterfly boom in a decade, with the overall number estimated to hit 150 million.

The Honghe Butterfly Valley in the Honghe Hani and Yi Autonomous Prefecture boasts more than 400 kinds of butterflies living in its year-round warm and humid environment.

Every year in May and June, a large number of butterfly larvae transform into butterflies in the valley. This year, the first batch of caterpillars pupated into adult butterflies on May 20, and the peak period is expected to fall between May 25 and June 10.

According to monitoring data, the number of butterflies in the Maguaitang, Pujiazhai and Niuchangping forests is more than three times that of the same period in 2020, the largest in a decade.

"The emergence of the butterfly boom is mainly a result of the local ecosystem," said Yang Zhenwen, a butterfly observer in the valley. 

 "The bamboo leaves that butterflies like to eat are abundant in the valley, which makes the butterflies reproduce massively and leads to a boom," Yang explained.

According to Yang, the butterfly boom is a special biological activity spectacle only seen in two places in the world. One is the Honghe Butterfly Valley, and the other is in Mexico.

 The butterfly boom is expected to last 20 days.