About Calosoma externum (Say, 1823)
Calosoma externum, commonly known as the narrow searcher beetle or churchyard caterpillar hunter, is a species of ground beetle belonging to the subfamily Carabinae. It was first described by Say in 1823. This species occurs across most of the United States, where it lives in fallow fields and can also be found near the margins of standing water. It has also been recorded from the northern shores of Lake Erie in Canada. Adult individuals of this species grow to a length of 28 to 35 millimeters, and have a black body with bluish iridescence along their margins. Adult Calosoma externum prey on caterpillars from species of the genera Melanoplus, Cirphis, Lachnosterna, Malacosoma, and Porthetria.
