Regulates ecdysteroidogenesis by direct innervation of the prothoracic gland by reducing cAMP production via the receptor for myosuppressin. The neurons that innervate the prothoracic gland during the fifth instar are most active during days 0-4, after which they reduce and then peak again on day 6. Expression suppresses the biosynthesis of steroid hormones called ecdysteroids that elicit molting and metamorphosis. Detected at the gland surface. Only expressed in the CNS and predominantly in the thoracic ganglia. Strongest expression is seen in two pairs of large neurons in each thoracic ganglion. These neurons are ventrolateral neurosecretory cells 1 and 2, they project their axons through transverse nerves into the periphery where axons from the prothoracic ganglion innervate the prothoracic gland. Expression is continuous throughout the developmental period, but is highest during the feeding period in the early half of the fifth instar stage (days 0-4). Expression decreases remarkably on day 5 before larvae start wandering on day 6, but stabilizes before the end of the fifth instar stage. RFa-1. RFa-2. RFa-3. RFa-4. Belongs to the FARP (FMRFamide related peptide) family.