Tiger moths, in general, are a distasteful insect anyway. They are primarily hunted by bats using sonar to locate their prey. These Tiger moths are capable of emitting a supersonic sound of their own which warns the bats, that have the experience, that this is coming from a potential distasteful meal and thereby avoiding being eating by the bat. O n the other hand all these nighttime fliers rest motionless during the day perhaps clinging to the bark of trees. This is where their protective colouration comes in.
Daytime predators use techniques that rely on vision to locate prey.
Some moths augment this camouflage with mimicry. While at rest it is virtually invisible but if danger does present itself the Io will display an eye pattern on it's hind wings by vigorously drawing forward it's forewings. This will frighten off, or at least startle, a predator that might have deciphered the protective colouration. By giving the appearance of a larger or even potentially more dangerous quarry that has just been disturbed or perhaps an opportunity to escape a second chance makes this an effective mechanism for survival. T hese are a couple of specific examples of both forms of deception but the principles remain the same.