The 24 solar terms calendar was devised by the ancient Chinese to match natural phenomena, and combined observations from astronomy, meteorology, biometeorology (which covers relationships between weather and living things) and agricultural experiences. In the past, farmers used the 24 solar terms calendar to forecast weather and predict crop yields. In light of that, we commenced Hong Kong's first research on the relationship between solar terms and butterfly ecology at two butterfly hotspots: Shing Mun Country Park and Tai Po Kau Nature Reserve.
The research allows us to obtain long-term data on solar terms and local butterfly ecology, such as species, abundances and behavior. Thus, the result contributes to the analysis and investigation of local butterfly ecology.
The research in Shing Mun Country Park and Tai Po Kau Nature Reserve showed significant fluctuations in butterfly species and abundance according to different solar terms, and the data collected in the two survey locations showed very similar trends. Our findings indicated that there is a relationship between abundance of butterflies and solar terms. Moreover, during the investigation, we also discovered that Shing Mun was located on the path along which Danaid butterflies arrive at their winter roosts in Hong Kong - i.e. Shing Mun is one of the locations on their migration routes.
Based on data from the past 10 years, there are three solar terms each year in which the numbers of butterfly species and individual butterflies will markedly increase. These three solar terms are “vernal equinox” (20th or 21st March), “corn on ear” (5th or 6th June) and “winter commences” (7th or 8th November).