Adipokinetic hormone (AKH) is a short peptide hormone that has been studied in insects. It is a lipid mobilising hormone and is responsible for regulating fuel transport in the haemolymph, for redirecting energy to other processes as required by the insect. AKH was initially discovered in the locusts Locusta migratoria and Schistocerca gregaria and is generally associated with aiding flight. Early observations of locusts showed that despite the fact that lipids are metabolised by flight muscle in order to maintain flight, which would be transported from the haemolymph, there was often still a high concentration of lipids in the haemolymph, implying that an agent may be responsible for activating lipid transport into the haemolymph and this was thought most likely to be hormonal regulation. The hormone itself is part of a larger family, often referred to as red pigment concentrating hormones (RPCH) discovered in crustaceans and the typical makeup of hormones in this family includes a length between 8 and 10 amino acids, blocked N and C termini, phenylalanine or tyrosine at position 4 and tryptophan at position 8. RPCH was discovered in crustaceans and shown to be involved in concentrating red pigments, for sexual displays and a variety of other reasons. The similarity between AKH and RPCH is so significant that injecting insects with RPCH induces an AKH like response and vice versa.