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


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.

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