Arctiine moths have tymbal organs on the sides of the thorax, thin ribbed cuticular plates that buckle when a muscle contracts, each buckling rib producing a click. A moth can emit hundreds to thousands of clicks a second in the ultrasonic range that bats use. The moth detects the bat first, using simple ears sensitive to those frequencies.
Three explanations have been tested. The clicks may startle a naive bat, may warn it that the moth is chemically defended, or may interfere with the bat's echo processing. Experiments in which naive bats learned to avoid clicking, distasteful moths support the acoustic aposematism reading for most species, and the startle effect fades with experience. Genuine sonar jamming has been demonstrated convincingly in the tiger moth Bertholdia trigona, whose click rate is exceptionally high, but it is not the general case.
Garden tiger caterpillars sequester defensive compounds from a wide range of herbaceous plants, and the adult retains them. British populations declined substantially in recent decades, a change associated with warmer, wetter winters, though the mechanism is not fully established.