Description: An 8-11mm long black ground beetle, externally indistinguishable from P. nigrita although in general smaller in size. Sometimes found with that species but in general prefers upland, exposed habitats.

NI account: Widespread and common in hill areas, at least in northern counties. Status elsewhere uncertain. Only verified records are included in the map.

Ecology: Best distinguished from P. nigrita on the structure of the male and female genitalia (Koch, 1986). It is generally smaller and more slender than that species and always uniformly dark. The two can occur together, as in the Erne River System of Fermanagh, but this is the exception rather than the rule. Our records indicate that P. rhaeticus is a cold-adapted species inhabiting exposed, nutrient-poor and upland environments while P. nigrita is primarily a lowland riparian species.

Distribution: A recent segregate of P. nigrita (Koch, 1986), found widely in Europe including the British Isles and Fennoscandia. Its wider distribution is poorly known, but almost certainly northern, and we provisionally classify it here as Eurosiberian Boreo-montane (44).

Similar Species: Pterostichus nigrita: slightly larger; aedeagus (male) characteristic (Fig. 99); (female) characteristic (Fig. 100) P. anthracinus; pronotum not denticulate; apices of elytra in female with sutural teeth P. minor/gracilis: pronotum not denticulate

Key Identification Features:

• Medium species, black
• Hind angles of pronotum sharp, denticulate
• Pronotum with two basal foveae
• Last abdominal sternite of male with a small tubercle
• Apices of elytra in female without teeth
• Aedeagus (male) characteristic (Fig 99); (female) characteristic (Fig. 100)

Distribution Map from NBN: Pterostichus rhaeticus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Pterostichus rhaeticus at iNaturalist World Species Observations database.

GBIF data for Pterostichus rhaeticus | Classification: Insecta, Coleoptera, Carabidae, Pterostichus

Thumbnails for genus Pterostichus