Photo:VCG

A valley in warm and mild Yunnan in Southwest China is expected to welcome more than 150 million butterflies in May and June in the largest "butterfly explosion" in 10 years, local ecology observers told media, attributing the phenomenon to a natural cycle as well as intact ecology.

The butterfly valley in Jinping Miao, Yao, and Dai Autonomous County has more than 320 butterfly species in 11 families, one of the most diverse butterfly habitats in the world. 

The valley is famous for butterfly explosion of Stichophthalma, better known as jungle queens. Each May and June, jungle queens come out of cocoons at the same time and people can see them flying in clusters everywhere. Some years see more butterflies and some fewer, and there is a cycle of six to seven years, Yang Zhenwen, a butterfly observer, told media on Friday. 

Based on the monitoring of eggs and cocoons over the past a few months, more than 150 million butterflies are expected to come out of their cocoons this summer, breaking a 10-year record.

As the temperature last year was higher than average, the creatures grew faster and the butterfly explosion this year comes five days earlier than usual. 

Yang also attributed the explosion to healthy ecology in the region as butterflies have high requirements on the environment. 

Continuous butterfly explosion suggested clean air and water, good biodiversity and ecology, and little human disturbance, observers said.

The valley attracted attention in 2009 when its butterfly resources were noticed. The county has a specific regulation that bans activities changing the river system, use of pesticide, and cutting of trees or bamboos.