A study focusing on the population structure of Euphyllura olivina (Costa, 1839) (Hemiptera: Aphalaridae) in olive groves of three regions of Kabylia (Algeria). We identified, for the first time, the existence of colour polymorphism in this olive tree pest. Two different forms have been identified in three distinct groves both in 2014 and 2015. The morphological variations affect different parts of the adult body of both sexes, including the abdomen and the terminalia.