Carabidae, Coleoptera, Insecta, Arthropoda, Animalia
Matthew Denton, The Evergreen State College, Olympia, WA 98505 USA.
01 April 1997
|Key to spp. | species list | genus key|
Identification
Pterostichus is one of the largest genera in the Carabid family, with over 200 species in 25 subgenera. Members vary in size but usually have a uniform appearance, being stout with short appendages. Mentum tooth emarginate at apex (except for honestus group); inner lobe of the maxilla prolonged into a heavily sclerotized, arched, inwardly directed tooth which appears hooked; terminal segment of all palpi cylindrical or fusiform; antennae pubescent from and including the fourth segment; prothorax with single or double laterobasal fovea and with two lateral setae; elytral epipleura crossed. Most species with abbreviated scutellar stria with an ocellate puncture at its base; first metatarsal segment usually with external furrow.
Range
Holarctic
Natural History
Variation in habitats wide; species are hygrophilous. Majority live independently of open water; some xerophilous, inhabiting open country such as prairie and tundra; others pronounced forest insects. Within the genus there are true subterraneous forms with depigmented cuticle and reduced or lacking eyes.1a. Elytra with at least one setigerous dorsal puncture on third interval (or on an adjacent stria). P. melanarius
1b. Elytra without dorsal punctures 10
10a At least first metatarsal segment with a sharp longitudinal ridge externally. 20
10b Metatarsi without ridge externally; largest species of the genus. P. lama
20a Last tarsal segment setose underneath. 30
20b Last tarsal segment glabrous underneath. 40
30a12-16 mm long; prothorax with small, rounded external foveae at base; posterior marginal puncture touching hind angle P. algidus
30b Less than 12 mm long; prothorax with single, linear laterobasal fovea; posterior marginal puncture widely removed behind angle. P. pumilus
40a Prothorax with sides crenulate almost to front angles; microsculpture absent on head and center of prothorax P. crenicollis
40b Prothorax with side margin smooth or faintly irregular near base; microsculpture evident also on head and center of prothorax. 50
50a Prothorax with front angles strongly protruding, triangular; outer basal fovea deep, sharply delimited externally; purple reflection absent. P. herculaneus
50b Prothorax with front angles much less prominent, outer basal impression obsolete or lacking; occasionally with purple reflection. P. amethystinus
References
Kavanaugh, D. H. 1992. Carabid beetles (Insecta: Coleoptera: Carabidae) of the Queen Charlotte Islands, British Columbia. Memoirs of the California Academy of Sciences Number 16. California Academy of Sciences, San Francisco, California, USA.
Lindroth, C. H. 1961-1969. The ground beetles (Carabidae excl. Cicindelinae) of Canada and Alaska. Parts 1-6. Opuscula Entomologica xlviii + 1192 pp.For information about this page: John T. Longino longinoj@evergreen.edu
Last modified: 04/01/1997