Aspects of the reproductive behaviour and physiology in three North American Gomphidae species (Anisoptera)

Field and laboratory observations on the reproduction of Gomphus externus, G. graslinellus and Progomphus obscurus are presented from Illinois, United States. Mating of G. externus in the field took 12 min. 2 phases were distinguished, the first consisted of tapping movements of the cj hamulus, the second of pumping movements of the cf abdomen. The ovary yielded 5100 eggs of which 690 were laid during hand-held oviposition in the laboratory. Only eggs laid by the $ but not the ones dissected from the ovary developed a sticky jelly coat around themselves. Eyespots of developing embryos were visible after 13 days. This 5 had stored approximately 200 thousand sperm (about 160 bundles) in her spermalheca. The sperm were still mobile 3 days after mating. A comparison of the penis horn length and the length of the spermathecal tubes revealed that <J <J cannot reach the end of the spermathecal tubes. A G. graslinellus 2 was observed to employ the dipping mode of oviposition. After oviposition she had approximately 1 million sperm remaining. 2 2 of both spp. showed no muscle contraction response when the cerci were touched with water, but responses to water differed between the 2 2 on segments 9 and 10. 6 P. obscurus perched on the sandy ground along the bank without territorial behaviour though 3 3 were observed to follow other 3 3 . The penis morphology of P. obscurus was similar to members of the genus Gomphus.