Infiltration by unwelcome strangers

Seven years ago I nearly put pen to paper (but not quite) to express my alarm at Dennis Paulson’s report of Crocothemis servilia (Dru.) in Broward and Dade Counties in Florida, (D.R. PAULSON, 1978, Notul. odonatol. 1: 9-10, 29- 30). Because it has resisted the attractions of the New World subtropics for many million years, its appearance now can only be attributed to human intervention. Unfortunately C. servilia is one of the most modern, efficient, adaptable flying machines in the subtropics of the Old insect-World and I expected a rapid spread in Florida. Jerrell Daigle now describes exactly that (J.J. DAIGLE & R.P. RUTTER, 1984, Notul odonatol. 2; 63); a spread of up to 150 miles is established already. By the nature of things, this has to be at the expense of New World species because we can assume there are no niches kept vacant for visitors. What local species will suffer? The whole thing should be viewed as a very serious matter. In Europe there are at least several similar cases known (for references cf. P. VALTONEN, 1985, Notul. odonatol. 2: 87-88); in Britain, Erythemis simplicicollis (Say) recently appeared (Mr Steve Brookes, pers. comm.) but indoors. These foreigners come in imported water plants for decorating fish tanks. Pretty water plants are mainly tropical and Britain is freezing (at the time I write this) so our uninvited guests will not settle to breed here; it is a different matter in Florida. What can be done about this insidious ecological mess-up?