Proposed as a subspecies of Hyloicus pinastri. Synonymized with Hyloicus morio as a subspecies by Derzhavets, 1979, Ent. Obozr. 58: 114. Inoue, 1982, in Inoue et al., Moths of Japan 2: 318, who was probably unaware of Derzhavets' paper, treated arestus as a subspecies of Sphinx pinastri. Reinstated implicitly as a subspecies of Hyloicus morio by Owada & Kishida, 1992, Mem. natn. Sci. Mus., Tokyo 25: 168. Implicitly synonymized with Hyloicus pinastri as a subspecies by Zhu & Wang, 1997, Fauna Sinica Insecta 11: 201 (key), 202. Implicitly synonymized with Hyloicus morio morio by Danner, Eitschberger & Surholt, 1998, Herbipoliana 4(1): 56. Reinstated as a subspecies of Sphinx morio by Kitching & Cadiou, 2000, Hawkmoths of the world: 68.
Scratchpads developed and conceived by (alphabetical):
Ed Baker,
Katherine Bouton
Alice Heaton
Dimitris Koureas,
Laurence Livermore,
Dave Roberts,
Simon Rycroft,
Ben Scott,
Vince Smith
