{{short description|Species of beetle}} {{Speciesbox | image = Ground Beetle (Calosoma Externum) (8076119611).jpg | taxon = Calosoma externum |authority=Say, 1823 | synonyms = *''Carabus externus'' <small>Say, 1823</small> *''Calosoma longipenne'' <small>Dejean, 1831</small> }} '''''Calosoma externum''''', the '''narrow searcher beetle'''<ref>[https://www.inaturalist.org/taxa/215911-Calosoma-externum iNaturalist]</ref> or '''churchyard caterpillar hunter''', is a species of ground beetle in the subfamily of Carabinae.<ref name=catlife>{{Cite web| title=Calosoma externum (Say, 1823) | url=https://www.catalogueoflife.org/data/taxon/Q38M | website=Catalogue of Life | access-date=2023-04-08 }}</ref> It was described by Say in 1823.<ref name=catlife/> This species is found in most of the United States, where it inhabits fallow fields and may also be found around margins of standing water. The species has also been recorded from the northern shores of Lake Erie in Canada.
Adults reach a length of 28-35 mm and have a black body with bluish reflections on the margins.
Adults prey on caterpillars of ''Melanoplus'', ''Cirphis'', ''Lachnosterna'', ''Malacosoma'' and ''Porthetria'' species.<ref>[https://www.calosomas.com/Callitropa/cal_externum.html Calosoma of the world]</ref>
==References== {{Reflist}}
{{Taxonbar|from=Q5023736}}
externum Category:Beetles described in 1823
{{Calosoma-stub}}