Pterostichus melanarius (Illiger, 1798)

Size: 13-17mm

Identification: Another of your stereotypical 'black beetles'. Body and appendage shining black. The best way of identifying this species is by its size and the fact that the  pronotum is evenly rounded but with sharp hind angles and a protruding tooth. Wings usually absent (winged individuals occur very rarely).

Habitat: Gardens, grassland and especially agricultural fields. Also often wanders into houses.

Lifecycle: Similar to P. madidus - an autumn-breeding species with some adults overwintering to breed again the following spring/summer. At higher altitudes all adults overwinter before breeding so that the lifecycle is biennial. A very useful predator of slugs.

Similar species: It is similar and usually co-exists with P. madidus, but is easy to separate as P. madidus has rounded hind angles to the pronotum whilst P. melanarius has pointed hind angles. P. melanarius is also normally slightly larger. P. melanarius prefers more open habitats than Pterostichus madidus and is commoner in non-basic grasslands and cultivated fields where is is often the dominant species.

P. melanarius can also be confused with Pterostichus niger, but this species is larger than P. melanarius without setae (hairs) underneath the claws at the end of the legs (P. melanarius has setae). Also, the side of the pronotum of P. niger are much straighter in front of the non-toothed hind-angles. If you find a large what you think is P. melanarius, it is worth taking it to check under a microscope or take a good quality photo of the pronotum and send it to me! Pterostichus cristatus is also similar, but is only found in northern England.

Pterostichus nigrita and Pterostichus rhaeticus have a similar pronotal shape but are much smaller (9-12mm).

Field/Lab: This species can be identified in the field with a hand lens.

Status in Pembrokeshire: Common and widespread.

UK status: Common and widespread.