Methyl farnesoate (MF) is a sesquiterpenoid (5 syllables… try to use it in a haiku!) hormone, meaning it has a 15-carbon skeleton.
Methyl farnesoate's carbon skeleton. Get it??
It is produced in the mandibular organs which are glands, kind of like our pituitary gland. It is the crustacean reproduction hormone, but the tricky thing about it is that MF is also related to the insect juvenile hormone. What does that mean? When a juvenile crustacean, like a crayfish, has a high level of MF in its system before molting, it WON’T molt to a mature/reproductively active state. It will stay a juvie. It’s like your average 13-year-old boy (or 23-year-old boy…): hormones raging, but still basically an infant.