O. ferrum-equinum was first described by Desfontaines from the Greek island of Samos in 1807 and its name refers to the horseshoe shaped speculum pattern which also gives it the common name of the Horseshoe Orchid.

This species has a localized but wide distribution in the eastern Mediterranean, centred on Greece but reaching as far as Albania to the North, Crete to the south and Anatolia to the east. Although as has been mentioned, it is very local, it can be abundant in its preferred locations, sometimes forming drifts of thousands of flowers. 

O. ferrum-equinum readily hybridizes with other nearby Ophrys and this tendancy, coupled with the species natural variation can often contribute to identification difficulties. Several forms and varieties have been formally recognized and "subtriloba" is amongst the most frequently encountered. As has been mentioned above, O. ferrum-equinum is hugely variable and as a species its nomenclature and the taxonomic positioning of the various forms is the source of considerable botanical debate.

O. ferrum-equinum f. subtriloba is recognizable by its lip shape, which as its name suggests, is a three lobed form, with lateral lobes that can often appear distinctly arm like. It always occurs among colonies of the nominate species and although this can be anywhere within that range, it seems to be at its most frequent in the Cyclades. In 2001, small flowered, three lobed plants from the Cycladic island of Anafi were formally described and named O. ferrum-equinum var anafiensis but it is suspected that these are actually conspecific with var. subtriloba.