Some bugs are capable of producing a foulsmelling chemical from glands in the sides of their bodies, especially the group known as Stink Bugs. This disagreeable odor turns away predators, but has no staining effect to humans. The Common Milkweed Bug has bright orange and black colors, and feeds on milkweed plants. These colors are a warning to vertebrate predators that the bug is poisonous, with milkweed plant toxins. Although sound making in insects is generally restricted to katydids and their relatives, and cicadas, some Assassin Bugs can produce hissing sounds by rasping their feeding tube against the underside of their body.
Many true bugs are aquatic.
Bugs of the Family Notonectidae are known as Water Boatmen, and are capable predators of other insects on the water surface. They detect the ripples of other insects on the water and run quickly to capture and kill the prey. Water scorpions are true bugs in the Family Nepidae that have long breathing tubes on their rear ends, which enables them to breathe air while still under water. They can survive in warm ponds or polluted waters low in oxygen. Selected References Blatchley, W. S. 1926.