This species is endemic to Croatia, having a limited distribution in Istria and the larger islands of the Quarnero archipelago. It is the last of the Croatian Spider Orchids to flower, coming into bloom in May, at least three weeks after the very similar O. tommasinii.  Unlike this latter Ophrys, it is a rare species, being found very locally in short grassland, open woodland and abandoned terraces on calcareous substrates. Confusion with either O. liburnica or O. incantata is improbable due to differences in both range and flowering times.
O. illyrica will frequently be found growing alongside O. tommasinii and despite the limited overlap in flowering periods, hybridization is well known and identification can be complicated. There are however some features that although not completely or solely characteristic of O. illyrica, seem more pronounced in this species as compared to O.tommasinii. These include, the broader yellow lip margin, smaller pseudo-eyes, less thick marginal hair and most importantly complete lack of prominent basal swellings.

A further key identification feature is the size of the basal field below the stigmatic cavity, which in this species is demarcated by a shallow semi circle above the speculum. In O. tommasinii the basal field is deeper and extends further into the specular pattern. We must stress again however that these two species are very similar and flowering times seem to be the only completely satisfactory way to separate them.