Adults but not nymphs of green mirid, Creontiades dilutus (Stål) (Hemiptera: Miridae) are sometimes detected in Tasmania. The species has been recorded, as adults at least, from a wide range of habitats, localities and plants in mainland Australia and suitable host plants occur in Tasmania. Most Tasmanian detections of C. dilutus have been in a long-term light trap and coincide with movements of known long-distance migratory insects and airflows favourable for migration across Bass Strait. In contrast adults and juveniles of the potato bug Closterotomus norwegicus (Gmelin) (Hemiptera: Miridae) are collected regularly in crops for which details are given. A published degree-day development model for C. dilutus was used to identify several impediments to fecundity, egg and juvenile survival and adult maturation such that even ephemeral seasonal establishment is highly unlikely. The absence of juveniles, coincidence of adults with migratory insects and northerly airflows and modelled obstacles to breeding in combination indicate that C. dilutus migrates to Tasmania. The results provide another example of a pest that fails to establish, even ephemerally, in Tasmania despite repeated migration from mainland Australia. Publications stating that the distribution of C. dilutus includes Tasmania are based only on captures of migratory adults. Climate matching models are prone to error if they assume C. dilutus is resident in Tasmania.