The delimitation of Amastus versus Hemihyalea has long been problematic. It was recently determined that the type species of Hemihyalea (the old Phaegoptera cornea) is so closely related to that of Amastus
(P. collaris) as to warrant inclusion in the present genus. That determination led to the reestablishment of the genus Pseudohemihyalea for the more distantly related group of species around "Hemihyalea" schausi. There is no consensus yet on whether to include the remaining Hemihyalea species in Amastus.[1]
"A." lehmanni as described by Walter Rothschild in 1910 is now in Opharus. The homonymous species described by Rothschild in 1916, now renamed "A." popayanensis, is one of those disputed between Amastus and Hemihyalea.
Pitkin, Brian & Jenkins, Paul (November 5, 2004). "Amastus Walker, 1855". Butterflies and Moths of the World. Natural History Museum, London. Retrieved September 9, 2019.
Pitkin, Brian & Jenkins, Paul (November 5, 2004). "Hemihyalea Hampson, 1901". Butterflies and Moths of the World. Natural History Museum, London. Retrieved September 9, 2019.
Pitkin, Brian & Jenkins, Paul (November 5, 2004). "Amastus Walker, 1855". Butterflies and Moths of the World. Natural History Museum, London. Retrieved September 20, 2019.
Savela, Markku. "Amastus Walker, 1855". Lepidoptera and Some Other Life Forms. Retrieved September 9, 2019.