Semiochemicals, terpenoids

The repertoire of chemicals that can be used for communication is limited by the biosynthetic ability of the insect. Compared to other insect orders, pheromone biosynthesis in Hymenoptera has received little study [191]. However, the biosynthetic origins of chemically diverse hymenopteran semiochemicals likely include aromatic, fatty acid, and terpenoid pathways as well as simple modifications of host-derived precursors. Notable recent studies include the biosynthesis of the fatty acid components (2 )-9-oxodec-2-enoic acid 52 and (2 )-9-hydroxydec-2-enoic acid of the honeybee queen mandibular pheromone from octadecanoic acid [192,193], and the aliphatic alcohol and ester... 

A variety of other plant compounds are bioactive as toxins, pro-toxins, sweet or bitter tas-tants, odorants, semiochemicals, enzyme inhibitors, receptor agonists, receptor antagonists or psychoactive agents. The structure and bioactivity of non-alkaloid, non-phenolic and non-terpenoid plant compounds is briefly reviewed below. Some selected structures of cyclic compounds in this category are shown in the Appendix (Section 4). 

The volatility of the lower terpenoids makes them particularly suitable for signaling between living organisms, as they can be carried through the air from the donor to the recipient of the signal. Such materials (semiochemicals) can carry messages between organisms of the same species (pheromones) or of different species (allelochemic als). 

---