Bombardier Beetle - Brachinus medius
Family Carabidae - Ground and Tiger Beetles
Live adult beetles photographed in the wild at San Antonio, Texas, USA. Beetles Main | Beetles Index
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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 sound as the beetle shoots, similar to a bursting balloon."  --From Wikipedia, the Free Encyclopedia

Whoops! This ground beetle gets captured by a Venus fly-trap plant.

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Order Coleoptera: Beetles are the dominant form of life on earth: one of every five living species is a beetle. Coleoptera is the largest order in the animal kingdom, containing a third of all insect species. There are about 400,000 known species worldwide, ~30,000 of which live in North America.  Beetles live in nearly every habitat, and for every kind of food, there's probably a beetle species that eats it.
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