Dragonfly behaviour over shining surfaces

(Comment on P. CRUCCITI, 1980, Notul. odonatol. 1: 89- 90) Crucitti’s description of dragonfly males touching the water surface briefly upon arrival, reminded me of my own observations of the same behaviour in at least three zygopterans (Coenagrion pulchellum, Enallagma cyathigerum, Pyrrhosoma nymphula, and possibly Ischnura elegans). During my field work in Wellemeersen, Belgium (M. VAN NOORDWUK, 1978, Odonatologica 7: 353- 374) I noticed Coenagrion males slipping with the abdomen through the water, and speculated on the significance of this behaviour. Dragonflies primarily have a visual orientation and are attracted to shiny surfaces, so they may need a check as to the oviposition suitability of the substrate. In the summer of 1974 I observed the same in Pyrrhosoma and Enallagma in a moorland at Bentheim, German Federal Republic. On this occasion we tried to analyse this behaviour further by putting plastic sheets (2x3 ra2) on top of Sphagnum bog, and counting dragonflies flying above this and observing their behaviour. Although the flight activity above the plastic was significantly higher than above control plots without plastic, we could not confirm the "touching" behaviour for this situation. I reported these observations at the Fourth Meeting of Dutch Dragonfly Workers, Utrecht, December 14, 1974 (cf. 1974, ContaciBr. ned. Libellenonderz. 13: 37), but was never able to follow it up afterwards. The movements are very rapid and they are easily overlooked.