Juvenile hormone III is an acyclic sesquiterpenoid that regulates diverse processes in insects, including adult transition of larvae and oogenesis in adult females. [1][2] It activates the juvenile hormone receptor, known as methoprene-tolerant, with a Kd value of 2.9 nM.[2] Juvenile hormone III can be synthesized from farnesoic acid by two alternative pathways, one through methyl farnesoate and the other through juvenile hormone acid III.[3][4]

Reference:
[1]. Tillman, J.A., Seybold, S.J., Jurenka, R.A., et al. Insect pheromones--an overview of biosynthesis and endocrine regulation. Insect Biochemistry and Molecular Biology 29(6), 481-514 (1999).
[2]. Charles, J.P., Iwema, T., Epa, V.C., et al. Ligand-binding properties of a juvenile hormone receptor, methoprene-tolerant. Proceedings of the National Academy of Sciences of the United States of America 108(52), 21128-21133 (2011).
[3]. Defelipe, L.A., Dolghih, E., Roitberg, A.E., et al. Juvenile hormone synthesis: "Esterify then epoxidize" or "epoxidize then esterify"? Insights from the structural characterization of juvenile hormone acid methyltransferase. Insect Biochemistry and Molecular Biology 41(4), 228-235 (2011).
[4]. Navare, A.T., Mayoral, J.G., Nouzova, M., et al. Rapid direct analysis in real time (DART) mass spectrometric detection of juvenile hormone III and its terpene precursors. Analytical and Bioanalytical Chemistry 398(7-8), 3005-3013 (2010).