Half-open collection intervals allow both signs of mean catch date change at six Finnish moth traps in 1993–2019

We tested whether recorded collection intervals fix the sign of a seasonal moth date change. We used the same 71 trap-years and 928 common species-trap pairs as a prior SCI study. The panel has six southern Finnish light traps in 1993–2002 and 2010–2019. Spreading catches evenly within each interval reproduces a 4.46-day delay. We kept catches, sampled years, species and monthly effort weights fixed. We then allowed capture times to vary within each recorded half-open interval. Sharp bounds on the equal-trap mean change were −5.81 to +14.94 days. These are fixed-sample time bounds, not confidence intervals. An added control kept each event’s allocated monthly catch fixed. Its range was −2.60 to +11.53 days. All-species and unweighted checks also allowed both signs. An independent linear program reproduced all 24 primary extrema. The result shows that the intervals alone do not establish the direction of this index change. It does not establish an advance, a national trend, or a climate cause. We preserve compact source data, provenance, code, figures, checks and offline reproduction instructions.

moth · phenology · interval data · partial identification · Finland · biodiversity monitoring