Sir please don't really get the isoprene unit for the cyclic terpens. The example you gave, can the isoprene unit be identified in the opposite direction??
0:10 Note that a pheromone is any chemical compound that carries a signal from one animal or plant to another, which then causes a physiological or behavioral change in the recipient. Ants marking a trail are an instance. While some pheromones are terpenes, other molecules are used for this purpose as well; they tend to be volatile, as the signal is often carried through the air.
