O. colossaea is a recently described species whose presence on the island of Rhodes was first formally recognized by Delforge in 2006. Up until that time the plants in question were thought to be O. episcopalis, although Delforge had already appreciated, when preparing his 2005, third edition, that this was not the case and linked the species with O. calypsus under the synonym of O. maxima. Its name is a reference to the famous and huge, erstwhile statue of the Colossus of Rhodes, an appropriate name for a giant of the Ophrys genus.

This species was placed within the O. heldreichii group and although at present only known with certainty from Rhodes, very similar plants, flowering at the same time have been discovered in Anatolia that may well prove to be O. colossaea. It is also entirely possible that this species may be present on other of the Aegean islands. This is a tall Ophrys (up to 70cms) with characteristically large flowers that serve as an important diagnostic marker when trying to identify it. Another significant indicator is its flowering period, which does not commence until at least the second week of April when O. calypsus and O. pseudoapulica although present will be past their best. The Rhodes endemic O. halia is also a later flowerer but its distinctive appearance makes confusion unlikely.

O. colossaea can be a variable species but typically the median lobe is trapezoid and lacks the "pot bellied" appearance of O. calypsus. Sepals are distinctively long and triangular with concolourous, pink petals. Labellum colouration ranges from chestnut to a deep mahogany red with a large sometimes compilated specular pattern. The pictures are from Rhodes and date from the end of April, at which time they were in full flower.