Calosoma externum

Say, 1823

Narrow Searcher Beetle, Churchyard Caterpillar Hunter

Calosoma externum is a large predatory in the , commonly known as the narrow searcher or churchyard hunter. First described by Thomas Say in 1823, this is notable for its hunting , ascending trees to on caterpillars. reach 28–35 mm in length and are distinguished by their black bodies with bluish marginal reflections. The species occurs across much of the United States and into southern Canada.

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Pronunciation

How to pronounce Calosoma externum: /kəˈloʊsəmə ɛkˈstɜrnʊm/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from similar Calosoma by its black coloration with bluish marginal reflections rather than metallic green, purple, or tones seen in such as C. scrutator (fiery searcher) or C. sayi (black hunter). C. externum is smaller than C. scrutator and lacks the intense purple pronotal coloration of that species. The specific epithet 'externum' refers to the marginal (external) coloration.

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Habitat

Inhabits fields and margins of standing water. Also found in upland forest areas during , where it ascends trees to hunt.

Distribution

Most of the United States; recorded from northern shores of Lake Erie in Canada.

Diet

on of several , including Melanoplus, Cirphis, Lachnosterna, Malacosoma, and Porthetria.

Host Associations

  • Melanoplus -
  • Cirphis -
  • Lachnosterna -
  • Malacosoma -
  • Porthetria -

Behavior

that actively climbs trees to hunt . are fast-moving and difficult to approach for photography. When captured, may release defensive chemical secretions.

Ecological Role

of ; may contribute to control of such as cankerworms and .

Human Relevance

for of pests. May be attracted to lights at night. Can release defensive chemicals when handled that linger on skin.

Similar Taxa

  • Calosoma scrutatorLarger size (25+ mm), more elongated and , intense purple central pronotal coloration; C. externum is smaller with bluish rather than purple reflections.
  • Calosoma sayiAll black without bluish reflections; lacks marginal coloration characteristic of C. externum.
  • Calosoma wilcoxiSmaller cousin of C. scrutator with different color pattern; C. externum distinguished by specific marginal bluish reflections.

More Details

Taxonomic History

Described by Thomas Say in 1823, one of the earliest .

Etymology

The specific epithet 'externum' refers to the external/marginal bluish coloration of the body.

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Sources and further reading