When exposed to volatiles from conspecific plants infested with caterpillars, undamaged plants became more defensive against caterpillars that may come in the future. This is called plantto-plant communication mediated by infested plant volatiles. An intriguing question is how uninfested plants smell volatiles. In communication between tomato plants, the amount of (Z)-3- hexenylvicianoside (HexVic) (glycoside of (Z)-3-hexenol) increases in the exposed plants, and this compound negatively affects the performance of caterpillars. The aglycon of HexVic, (Z)-3-hexenol, is transmitted in the air from the neighboring infested tomato plant. Glycosidation of airborne alcohol is commonly seen in many plant species. Thus, glycosidation is one of the mechanisms involved in the volatile reception (smell) in plant-to-plant communication.