What it looks like: 5-8 mm in length. 4.0-4.2 mm in width. Wing-covers blue with highly defined ridges, lacking dense hair. Head, pronotum (dorsal part of the thorax), abdominal segments, and antennae reddish brown.
Where you'll find it: Coasts, plains, and mountains of southwestern North America.
Natural History: Much in regard to the lifestyle of B. costipennis is unknown or unverified. B. pallidus, which is very similar to B. costipennis, has been studied more rigorously. Because of their likeness, we can assume that B. costipennis has a lifestyle similar to that of B. pallidus in that it is a generalist predator and scavenger. It also can be assumed to be a parasite of the pupae of streamside insects in its larval stage, but the species of insects that it has a parasitic relationship with is not known.
It is present mainly in sand surrounding streamside areas or under moist, jagged rocks. Usually not found in the harder to reach areas that other Brachinus occupy, but can fit into small crevices, so it can be hard to spot.