Adult peacock butterflies, Aglais io\textit{Aglais io}Aglais io, have wing spans ranging from 50 mm to 63 mm in a woodland population.
Which of the following correctly describes this variation in wing span among these butterflies?
Interspecific and controlled by genetic factors only
Intraspecific and controlled by genetic factors only
Intraspecific and controlled by both genetic and environmental factors
Interspecific and controlled by both genetic and environmental factors
