- Abstract SYNOPSIS. Similar to juvenile hormone production in adult insects, the production of methyl farnesoate (MF) seems to be related to reproduction in both sexes in mature crustaceans. The mandibular organ (MO) synthesizes MF, and its activity corresponds to reproductive stages. High MF levels in the blood are found in vitellogenic females and reproductively active males. Conversely, low levels are found in immature females, non- vitellogenic females, and males that are in reproductive diapause. The MO is under inhibitory control by neurosecretory factors from the sinus gland located in the eyestalks, and may be stimulated by factors from the brain and/or thoracic ganglion.