Behaviour of dragonflies during the 2009 partial solar eclipse in Japan (Odonata: Libellulidae)

Abstract

Behaviour of dragonflies was observed during the partial solar eclipse in Saitama, Japan, on 22 July 2009. The solar eclipse started at 09:54 h, reached its maximum magnitude of 74.9% at 11:12 h, and ended at 12:29 h. Light intensity at the peak of the eclipse was 1005 lx, a reduction by 28.2% of that at the start, and the ambient temperature was rather constant because of cloudiness. Dragonflies were active until immediately before the eclipse maximum and thereafter ceased their movements; one Orthetrum albistylum speciosum male perched atypically with its body axis nearly parallel to its perch. They resumed activities after a long delay, c.40 minutes after the peak. One female of Pseudothemis zonata oviposited near a perching male soon after the peak, but the male did not interfere with it. The inactivation of dragonflies in a solar eclipse may be related to the light intensity.

Keywords:

• Odonata
• dragonfly
• solar eclipse
• inactivity

Acknowledgements

I wish to thank Dennis Paulson and Michael May for correcting and critical reading of my text, Hiroji Naraoka for his critical reading, Naoji Katatani for his offer of his observation data, Martin Schorr for sending me literature and Satoshi Ohori of Waseda University for permitting my observation at Mikajima campus.