Most species of ground beetles are predators so they are considered beneficial. The bombardier beetle has a dark body with reddish yellow or orange head and legs. It inhabits all continents except Antarctica. They commonly live under shoreline debris. They are parasitoids of whirligig beetle pupae so they tend to live near bodies of water frequented by the whirligig beetle.
The bombardier beetle is only 4-15 mm. in length—usually less than inch long-- but has the most marvelous defense mechanism. It draws two liquids from two different chambers in its abdominal area and mixes them in a third chamber, creating a chemical reaction. When threatened by a frog or spider or ant, it blasts out from its back end and the resulting acid mixture is 212 degrees F. The beetle can aim two nozzles in many directions and while the resulting spray is not a serious threat; the vertebrates, such as humans, it can burn and stain your fingers and will scare off most of the beetle’s predators.
Scientists and photographers have gotten together and filmed the bug blasting away and its action can be seen on YouTube. How amazing.