CORBET: I should like to welcome you to the fifth of our plenary seminars. These have been a feature of S.I.O. International Symposia since the one held at Chur, Switzerland in 1981. These seminars, or discussion sessions, offer a good opportunity for us to exchange information and views on various topics in odonatology, especially those topics which may be elucidated by the exposure of chance or anecdotal observations, because such observations are unlikely ever to be published or shared with a large group of odonatologists; also, of course, there is the value of interaction among ourselves during these discussion sessions which is beneficial as long as it does not lead to cannibalism! I should like to thank Dan Johnson, Secretary of the Organising Committee, and members of the Committee for having asked me to chair such a session at this Symposium and also those who submitted suggestions for topics to be discussed in it.