Female of Papilio rex from Tanzania

Thanos is correct, and if you read the thread carefully my reply was agreeing with colin12303, who said that rex, commixtus and regulus [regulana] all look the same, and are all variable. I did not include mimeticus since Colin didn't either.

Ackery et al. 1995, Carcasson's African Butterflies lists the following subspecies for P. rex:

rex rex
(Highlands of north-eastern and central Tanzania)
rex abyssinicana (= abyssinicus, junior homonym)
(Highlands of south-eastern Ethiopia)
rex commixtus
(Kenya highlands west of the Rift Valley)
rex franciscae
(Mountains in southern Sudan and in south-west Ethiopia)
rex mimeticus
(Uganda, Zaire (Ituri, Kivu), Rwanda, Burundi and north-west Tanzania)
rex regulana (= regulus, junior homonym)
(Kenya highlands, east of the Rift Valley)
rex schultzei
(Cameroon highlands and eastern Nigeria)

Note that after listing the nominate subspecies the rest are treated in alphabetical order, not by distribution.

Of these 7 subspecies, probably regulana at least is a synonym of rex, and commixtus is not really different when considered in series. Subspecies mimeticus is generally distinguishable from true rex, and the remaining subspecies seem valid. This means there are really 5 subspecies of Papilio rex.

Adam.