Thanks Samaneh for your nice question. Monoterpenoids are typically found and widely distributed in higher plants and possess a basic skeleton of 10 carbon atoms.
Monoterpenes are volatile, lipophilic, and give characteristics odors to many plants. These compounds accumulate in resin ducts, secretory cavities, and epidermal glands. They are important constituents of essential oils present in conifers, mints, composites, and citrus. Some commercial monoterpenes are menthol, camphor, and alpha-pinene.
One of the best examples of monoterpene derivatives which are toxic to insects are the pyrethroids found in the leaves and flowers of some chrysanthemum species. Pyrethroids are neurotoxins, causing hyperexcitation, uncoordinated movement and paralysis of insect.