These are the thickened, leathery, or horny front wings. The adults are commonly found under stones, logs, leaves, bark, debris, or running about on the ground. Most species hide during the day, feed at night, and commonly fly to lights. Adults and larvae are nearly always predaceous on other insects, and many are very beneficial. The larvae usually live in the same locations as the adults.
Many ground beetles give off an unpleasant odor when handled.
Brachinus species are called bombardier beetles because of their habit of ejecting from the anus a glandular secretion that literally explodes when released, producing a popping sound. This secretion is foul-smelling and irritating, and serves as a means of protection. Aphididae The aphids constitute a large group of small, softbodied, insects that are frequently found in large numbers sucking the sap from the stems or leaves of plants. Such aphid groups often include individuals in all stages of development. They secrete a defensive fluid.