Description and Biology
Most of the bombardier beetles have orange heads, thoraces, and legs. They are ground beetles, many with wing covers over the abdomen that are usually dark blue. Some ground beetles such as Brachinus fumans and others in the genus Brachinus and related genera use hydroquinones for defense. They secrete a mixture of hydroquinones from a glandular sac at the rear of the abdomen. When the beetles are perturbed, they are able to add hydrogen peroxide to the hydroquinones. Free oxygen is released explosively that heats and propels by products of the hydroquinones with an audible pop (hence the name bombardier beetles). Bombardier beetles can aim the extremely irritating expulsion with some degree of accuracy at their assailants and can repeat these discharges up to twenty times. False bombardier beetles, genus Galerita, use formic acid and acetic acid for defense. It takes about 5 days for a false bombardier beetle to replace the formic acid released in one burst.
Ground beetles tend to live for several weeks during which they mate and pass on their genes. Some bombardier beetles can survive for several years under ideal conditions. Ground beetles lay eggs in small underground tunnels or cracks of rotting wood or even in decomposing remains of other organisms. From the egg hatches a tiny larva that feeds feeds on hapless animals it encounters as it molts and grows. With the ultimate larval molt emerges the pupa, a non-feeding developmental stage. Eventually the pupa molts and a new adult bombardier beetle emerges. Bombardier beetles are sometimes gregarious and may congregate with others in hollow logs or other dark, damp places.
Bombardier beetles have not been reported as plant pests.
Because bombardier beetles prey upon other insects and small organisms, they are probably more beneficial than harmful in the home landscape. If a beetle is handled, keep it away from the face as their defensive expulsion of quinones is quite irritating to the eyes.
- Bombardier Beetles, Scientific Name Brachinus spp. Anonymous. No Date. National Wildlife Federation.
- Spray aiming in the bombardier beetle: Photographic evidence. Eisner, T. and D. J. Aneshansley. 1999. Proc. National Acad. Sci. USA. Vol. 96 (17): 9705-9709.
- Brachinus fumans. Poetker, E. 2003. Animal Diversity Web.
- Defensive production of formic acid (80%) by a carabid beetle (Galerita lecontei). Rossini, C. et al. 1997. Proc. National Acad. Sci. U S A. Vol. 94(13): 6792–6797.
- Extension Plant Pathology Publications and Factsheets
- Horticultural Science Publications
- North Carolina Agricultural Chemicals Manual
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This Factsheet has not been peer reviewed.
Publication date: Sept. 16, 2016
Revised: May 3, 2021
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