Local gene duplications in an ancestral arthropod created three allatostatin C genes.
These three genes code for three different peptides, allatostatin C, CC and CCC.
Horse shoe crabs, spiders, scorpions, myriapods and decapods have all three genes.
Most insects lost one gene, but migratory locusts and sawflies have still all three.
Some arthropods genome assemblies have contigs with all three genes still associated.