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Bombardier Beetle - Brachinus medius
Order Coleoptera Linnaeus, 1758 -- beetles, besouro, coléoptères / Suborder
Adephaga Schellenberg, 1806 / Family Carabidae Latreille, 1802 -- carabes,
ground beetles / Genus Brachinus Weber / Species Brachinus medius
Harris
Live adult beetles photographed at San Antonio, Texas, February 2003
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Bombardier Beetle Brachinus medius
Beetles in the family Carabidae are commonly known as ground
beetles; ground beetles in the tribes Brachinini, Paussini,
Ozaenini, and Metriini are commonly known as Bombardier Beetles,
after their most notable defensive attribute: the ability to
fire an explosive charge of noxious, corrosive chemicals from
special glands in their posterior.
"Secretory cells produce hydroquinones and hydrogen peroxide
(and perhaps other chemicals, depending on the species), which
collect in a reservoir. The reservoir opens through a
muscle-controlled valve onto a thick-walled reaction chamber.
This chamber is lined with cells that secrete catalysts and
peroxidases. When the contents of the reservoir are forced into
the reaction chamber, the catalases and peroxidases rapidly
break down the hydrogen peroxide and catalyze the oxidation of
the hydroquinones into p-quinones. These reactions release free
oxygen and generate enough heat to bring the mixture to the
boiling point and vaporize about a fifth of it. Under pressure
of the released gasses, the valve is forced closed, and the
chemicals
are expelled explosively through openings at the tip of the
abdomen. Each time it does this it shoots about 70 times very
rapidly. (The spray, aimed with precision, can be pointed in any
direction, including forward over its back. This by bouncing the
spray off a pair of skeletal reflectors stuck from the tip of
its abdomen at the moment of ejection.) This makes a loud
cracking or banging sound as the beetle shoots the spray,
similar to a bursting balloon."
--From
Wikipedia, the Free Encyclopedia |
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