Understanding the mechanisms behind the seasonal emergences of herbivorous insects is ecologically important. However, little is known about the effect of meteorological factors and the other individuals in cicada emergence timing in fluctuating environments. Particularly, due to the long lifecycle and subterranean larval stages of cicada species, investigating their seasonal outbreaks is difficult. 

To overcome this, we reconstructed a time-series dataset that consists of cicada emergence and meteorological factors, leveraging a long-term collection of cicada shells by the elementary and junior high school student. Then, we performed a modern nonlinear time-series analysis, which allowed us to investigate causal relationships between the time series. 

Our findings are three-fold: 1) the dynamics of the opposite sex were major drivers of daily cicada emergence and the effect was stronger in males than in females, 2) likely to other insect species, temperature measurements consistently affect cicada emergence, but those effects are relatively weak, and 3) precipitation and humidity were causally related to emergence. 

These results are consistent with their subterranean life cycle and the theory of sexual selection, demonstrating the importance of latent data collected by non-expert citizens for ecological studies.

The monitoring site was a public green space of approximately 2200 m2, surrounded by residential areas. The monitoring procedure was as follows: All the discovered cicada shells, except for molting individuals and those that failed to molt, were collected by an insect net between 6:00-8:00 AM. The monitoring was done every day from July 1 to August 31 and continued from 2003 to 2012.

The data from September 1 to June 30 from 2002 to 2012 was filled with NA values because virtually no cicada individuals emerged during this period.