Closely related to Small Square-spot (D. rubi) inhabiting fens and boggy ground. Fen Square-spot (D. florida) is supposedly separated from D. rubi by its larger size, paler hindwing and brighter more orange forewing. D. florida is also thought to be single brooded in the south, appearing between the two generations of D. rubi.
No genitalic differences have been established to separate D. florida from D. rubi and fertile hybrids are readily obtained. D. rubi is considered by some to be in the process of evolutionary separation and others speculate as to whether this is a true species.
Past records from Redgrave Fen, Burgh Common and other sites in the Broads are all subject to conjecture and varying opinions over their validity.
Any claims for Fen Square-spot (D. florida) must be accompanied by a voucher specimen and photographs. Further research is needed to clarify the complex situation.