Copulatory activity of I. elegans is described in a high-density population in the south of France, Copulations lasted for 324 ± 90 min (s.d.) with stage I occupying 239 ±112 min, and stage II, 85 ± 48 min. The characteristic movements of stages I and II are described. They differ from those in other zygopterans by being frequently interrupted by extended inactive pauses which account for the long duration of copulation. Long copulation may allow males to guard females until they are prepared to oviposit after 16:00 h. Close-up observations of copulations were made possible by crushing the heads of captured pairs: This allowed females to be dissected without interrupting copulation, and video films of the penis movements within the transparent genital tract of the female were made. Sperm removal from the bursa and the subsequent transfer of sperm from the male were witnessed. Movements of the penis were correlated with those of the second and third abdominal segments of the male. Ablation experiments showed that continuation of copulation depended only on the maintenance of contact between the ovipositor blades and recesses in the male, probably containing sensory bristles. Reflex responses of vaginal and spermathecal muscles were brought about by stimulation of vaginal campaniform sensilla by the penis. Pairs with crushed heads performed copulations without pauses and lasting about I h, as did tethered intact pairs. Similar short copulations also sometimes occur in the wild.