Evolution of the odonate copulatory process

Odonate copulation is almost unique among the Pterygota in that the primary genitalia do not meet during copulation. Previous explanations concerning the evolution of the odonate copulatory process have been influenced by phylogenetic schemes which consider the narrow-winged Zygoptera the most generalized Odonata, However, fossil evidence and the comparative morphology of recent Odonata indicate that the broad-winged Zygoptera represent the most generalized Odonata among recent forms, supporting general evolutionary trends toward male domination of the copulatory process, and toward completion of the copulatory process in flight. One group of scenarios explaining the origin of the odonate copulatory process assumes the original direct transfer of sperm between primary genitalia. These scenarios require that oviposition originally be in tandem, and that sperm transfer to and from the male anterior abdominal sterna originally be accidental. Scenarios assuming the original indirect transfer of spermatophores as in the Apterygota avoid such problems, and lead to an original copulatory sequence which, when slightly modified, is essentially that of existing Odonata. The proposed scenario differs from those previously put forward in that extraordinary postures are not envisioned, the process is originally completed at rest, and development of the odonate tandem hold occurs just prior to sperm transfer. The tapdem hold is considered to have developed to prevent female predation of the male while the male guided her to his spermatophores.