Variability in colour, metallic lustre, and body size of Carabus arvensis Herbst, 1784 (Coleoptera: Carabidae) in relation to habitat properties

Objectives are to elucidate whether populations of Carabus arvensis Herbst, 1784 from contrasting habitats differ in (i) colour, (ii) brightness of metal lustre, or (iii) body size (length of elytra, of elytra + pronotum, and width of pronotum). Two large populations were studied, originating from (a) open heathland, being a remnant from more widespread heaths during former centuries, and (b) mature pine forest established 100–150 years ago on sandy agricultural land. Heath individuals had significantly more brilliant metal lustre and mostly lighter, vivid copper colour than pine forest individuals, which were typically black with a violet shade and slightly larger in size. The two populations are nowadays isolated, which was probably not the case 1–2 centuries ago, when both sites studied were treeless. The usually blackish colour of the forest population could be a recent adaptation to the changed environment, though some influence of processes such as genetic drift cannot be excluded.