Field observations on sperm translocation behaviour in the males of Crocothemis erythraea (Brullé) and Orthetrum cancellatum (L.) (Libellulidae), with a review of the same in the Anisoptera

The main question about the little-known process of sperm translocation in anisopteran males, is whether sperm translocation is performed by the male alone and/or "in tandem". Systematic observations of the pairing in C. erythraea and O. cancellatum, from male-female seizure till starting of copulation, revealed that sperm translocation always occurred following tandem formation. The sequence (tandem seizure — sperm translocation — copulation) is suggested to be a behavioural chain in which each phase takes a rigid position. On this basis, the "in tandem" sperm translocation is considered to be the normal behaviour, while sperm translocation in the male alone is suggested to be anomalous.