Egg-laying hormone (ELH) acts as a neurotransmitter on neurons of the abdominal ganglion and as hormone by diffusing to the circulating hemolymph to modulate the activity of other organs. It specifically causes contraction of smooth muscle in the ovotestis and expulsion of the egg string. The peptide corresponds to aa 206-241 of ELH.H-Ile-Ser-Ile-Asn-Gln-Asp-Leu-Lys-Ala-Ile-Thr-Asp-Met-Leu-Leu-Thr-Glu-Gln-Ile-Arg-Glu-Arg-Gln-Arg-Tyr-Leu-Ala-Asp-Leu-Arg-Gln-Arg-Leu-Leu-Glu-Lys-NH2 or H-ISINQDLKAITDMLLTEQIRERQRYLADLRQRLLEK-NH2