The so-called ‘giant form’ of D. arcturi was considered by Gibson (1998, 1999, 2010) to be at least an ecotype, while Clayton (2003) thought that the two forms should deserve at least subspecific status; both authors suggested that further study was needed. However, the fact that both morphotypes occur together over such a wide geographic range and in the same habitats, but without apparent intermediate forms, suggests instead that they may be distinct albeit closely related species, as subspecies are generally regarded as being geographically (Schlauer 1996) and/or ecologically allopatric (Stace 1989).