Changes in the number of spermatozoa in the female sperm storage organs of Ischnura asiatica (Brauer) during copulation (Zygoptera: Coenagrionidae)

Spermatozoan dynamics in the 9 sperm storage organs of I. asiatica were examined with interrupted copulation experiments in the field. The copulation process was divided into 3 stages (I, II and III) according to the movements of the <J abdomen. 9 9 interrupted just after the termination of stage I of copulation contained a much lower number of spermatozoa, both in the bursa copulatrix and in the spermatheca, than solitary 9 9 captured before being attached by 6 3. At the tip of the 6’s secondary genitalia, there was a pair of horns which might be used to remove sperm from the bursa copulatrix and the spermatheca during copulation. The latter was joined to the base of the former by a spermatheca! duct. Since each hom of the <J genitalia was significantly shorter than the spermathecal duct, the spermatheca might be inaccessible to 3 6. The actual position of the horns in the 9 sperm storage organs during stage 1 of copulation was observed by freezing copulating pairs using quick-freeze aerosol sprays. The horns were in the bursa copulatrix, but no horns had entered the spermatheca. Additional mechanisms of sperm removal from the spermatheca are proposed.