Red-leg catch odds showed no clear change at three Alice Holt beetle trap lines between 1994–2003 and 2004–2013

We tested whether red- and black-legged Pterostichus madidus changed in relative pitfall catch frequency within fixed UK Environmental Change Network lines. Only Alice Holt met the coverage and coding rules. Three lines had 20 complete years and 720 sex-colour-season-year cells. We compared 2004–2013 with 1994–2003, with control for sex and season. The geometric mean red-versus-black catch odds ratio was 1.013. Its nominal 95% interval was 0.944–1.070 from 4,999 shared three-year block draws. The red-leg share changed from 61.99% to 62.12%, or +0.13 percentage points (−1.40 to +1.48). Planned quality, effort, coding, allocation and block checks retained the local null result. The data did not establish an increase or a decrease in the mean decade contrast. This is a catch result at one site, not a population or genetic result. Annual shares differed among lines. The package preserves raw data, provenance, a local plan and amendments, code, all results, figures and independent checks.

carabid beetles · Pterostichus madidus · leg colour · pitfall traps · ecological monitoring · activity-density · Environmental Change Network · null result