Twice in the past week I’ve seen hordes of narrow-winged damselflies (Odonata: Coenagrionidae) engaged in mating along nearby waterways. On Sunday there were many along Mill Lake at Waterloo State Recreation Area near Chelsea, Michigan. Then yesterday I saw even more along the Maumee River at Side Cut Metropark in Maumee, Ohio.
Damselflies have an interesting way of mating. Males produce sperm from the genital openings on their ninth abdominal segments, but their penises are on their third abdominal segments. For this reason their penises are considered “secondary genitalia.” They pass sperm from their genital openings to their penises by bending their abdomens forward. Once this is accomplished, a male will grasp a female behind her head with clasps on the end of his abdomen. The two will remain in tandem for some time (Triplehorn and Johnson 2005):
Eventually the two enter the “wheel position.” The female will bend her abdomen forward to receive the sperm from the male’s secondary genitalia (Triplehorn and Johnson 2005):
Damselflies usually initiate this position in flight, and land only to finish copulation (Triplehorn and Johnson 2005). Once a female’s eggs are fertilized she will lay them near a stream or pond. When the eggs hatch, the young nymphs enter the water and prey upon other aquatic animals. They don’t leave the water until their final molt into adults, and even then tend to stay near their aquatic nurseries.
Triplehorn, C.A. and N.F. Johnson. 2005. Borror and DeLong’s Introduction to the Study of Insects. Seventh Edition. Thomson Brooks/Cole, Belmont, CA.