The mean May–June beetle capture share change was uncertain at six UK ECN sites in 1994–2013

We tested the May–June share of May–October ground beetle captures at six UK Environmental Change Network sites. We compared 1994–2003 with 2004–2013 on 18 fixed trap lines. We used documented trap dates and quality flags to set effort to a common level. The primary set had 41 species and 113 species-line pairs with at least 20 captures in each period. Mean early share rose from 32.22% to 35.78%. The change was +3.56 percentage points, with a nominal 95% interval of −4.65 to +10.60 from 4,999 site and shared year-block draws. A standard exact split gave +2.96 points within species and +0.60 points from species composition. Both part intervals included zero. The parts had opposite signs on nine of 18 lines. The all-species change was +3.54 points and was also uncertain. All planned checks left the mean direction unresolved. The selected species retained 81.7% and 85.1% of the catch index on average, with much lower retention on some lines. This measure does not test activity onset or climate causes. Pitfall catches depend on animal numbers and movement. These selected sites do not represent all UK habitats. The package has unchanged source data, provenance, code, figures, all results, an independent source rebuild, and repeat instructions.

ground beetles · seasonal change · species composition · pitfall traps · Environmental Change Network · reproducible analysis · null result