A time-order check gave no clear current-versus-next spring slope difference for Meadow Brown dates in four English samples, 1976-2024

We tested whether Meadow Brown mean flight dates had a more negative link to current March-May warmth than to warmth in the next spring. Four site-effect models used 18,868 English site-year records in two regions and two periods from 1976 to 2024. Each model controlled linear time and fitted both temperature terms. Current-minus-next slopes were -3.83, -1.56, -5.60 and -2.43 days per degree C. Every interval included zero after adjustment for 12 planned tests. Count, site-trend, common-site, and year-omission checks kept the contrast direction. The data did not establish a clear difference in each sample. This does not show equal slopes or no climate response. Shared weather, few year clusters, unknown visits, selected records and coarse temperatures limit inference. The package gives code, aggregate evidence, a figure, and exact input hashes. Externally licensed records remain outside the package.

phenology · butterfly · negative control · temperature · observation bias · time specificity · null result