Plant semiochemicals play a decisive role in the tritrophic interaction of plant-herbivore-natural enemy. Plants produce a diverse array of physical and chemical traits that confer various types of resistance to herbivores. Besides physical defense organs and plant secondary metabolites (PSMs) as direct defense, when attacked by herbivores, plant could emit herbivore-induced plant volatiles (HIPVs) as signals to attract natural enemies of the herbivores, which have been interpreted as being indirect defenses. Avian insectivores coud also find insects through visual changes in low light reflectance of damaged foliage. Seabirds could use DMS which released by phytoplankton to locate foraging area.