Hormonal Control

Milkweed bugs on a milkweed pod

Juvenile Hormone (JH) is a hormone specific to insects that is involved in regulation of numerous precesses. Juvenile Hormone was originally named for its ability to suppress adult genes and maintain larval genes. In the presence of Juvenile Hormone, an immature insect will molt to a larger size immature. In the absence of Juvenile Hormone, adult genes are expressed, larval genes are suppressed and an insect will molt from a larva to an adult or a pupa.

Juvenile Hormone regulates other processes. In some insects, JH stimulates the production of yolk protein and the development of the female ovaries. Why does JH stimulate ovary development in adults but not larvae? A group of scientists* studied JH effects in the linden bug. They found that JH requires a receptor known as “Met” plus co-factors for activity. JH, Met and another co-factor called “Kr-h1” are necessary to prevent an immature bug from molting to adult. The development of the ovaries requires JH, Met and yet another co-factor, “Tai”. In the developing model, JH is the master signal. The fine control over which processes and tissues are affected requires the target cells to make appropriate co-factors. This allows JH to have specific effects on some tissues but not others.

*Niels Wynant, Dulce Santos, Rik Verdonck, Jornt Spit, Pieter Van Wielendaele, Jozef Vanden Broeck. 2014. Identification, functional characterization and phylogenetic analysis of double stranded RNA degrading enzymes present in the gut of the desert locust, Schistocerca gregaria. Insect Biochemistry and Molecular Biology, Volume 46: Pages 1-8,
http://dx.doi.org/10.1016/j.ibmb.2013.12.008.
(http://www.sciencedirect.com/science/article/pii/S0965174813002257)