April-May warmth gave no clear link to paired cicada song gaps in four Japan samples in 1953-2020

We tested whether April-May warmth changes the first-song gap of Meimuna opalifera minus Graptopsaltria nigrofuscata. We used 2,153 paired station-years at 39 Japan stations in 1953-2020. Four separate region and period models controlled station and report marks and year. Estimates were +0.75 to +4.23 days per C. All four 98.75% uncertainty intervals included zero and both signs. Checks for observation location, adjacent missing years, station trends and prior autumn warmth did not establish a common response. The result adds a reproducible paired-species panel and a focused null result. Unknown detection effort, coarse temperature data, persistent-record selection and weak northern precision limit biological inference. First-song gaps do not measure overlap of full calling seasons. The test does not address pollution or daily weather extremes.

cicada · phenology · temperature · observation bias · paired species · Japan · null result