Euphaea impar: the Blue-Sided Satinwing

During my four years as a young adult in Singapore, I spent most of my free time taking photographs of arthropods (and the odd reptile or amphibian) in the reserve forests of Singapore, which became my learning grounds. On one particular trip to the MacRitchie Reservoir Park I decided to venture off the trail and into a little stream, hoping to find some new subjects to photograph. It was a shallow, sandy stream, and quite heavily shaded by the forest canopy. My detour paid off, and I was exhilarated to find and photograph both a male and female individual of a beautiful species of damselfly: Euphaea impar.

Euphaea impar Selys, 1859 (male)

Euphaea impar displays a phenomenon known as sexual dimorphism, which means that the males and females are different in size, shape, and/or colour. The above photograph shows the striking blue thorax of the male; the photograph below shows how, in contrast, the female is more of a dull grey.

Euphaea impar Selys, 1859 (female)

The iucnredlist states that Euphaea impar is a widespread species, known from peninsular Malaysia, Sarawak , Sabah, Brunei , Kalimantan, the Anambas Islands, Bangka island, and Thailand (although it has only been recorded at one site).

While doing my research on the species on the Internet, I discovered that, in Singapore, Euphaea impar is probably the only extant species in the damselfly family Euphaidae (Davison et al, 2008).

Choong (2005) observed and documented an unusual and fascinating behaviour in this species: while the females of several other damselfly species slowly immerse themselves into water during oviposition (the process of laying eggs),  Euphaea impar females have been observed to actually dive from a height of about 20cm into running streams to oviposit on submerged rocks and plants up to depths of 10cm, and can stay submerged for 30 minutes.

Another unusual observation was that the females oviposited on their own, without the males clasping onto them. Typically, male damselflies remain attached to the females until the oviposition process has been completed (see my previous post).

It must be mentioned that this species — Euphaea impar — was described in 1859 (that is more than 150 years ago) by a man named Michel Edmond de Selys Longchamps, who is credited as being the founder of odonatology: the study of Odonata (Wasscher & Dumont, 2013). Selys, as he is referred to by biologists, described over 700 species of odonates under 134 genera, and pioneered the framework for the taxonomical classification of species under this incredible and fascinating order — Odonata.

I love learning about the subjects I photograph. On this occasion, I was fortunate enough to find AND photograph both the male and female of the species — an occurrence that does not take place very often. In any case, do subscribe to my blog if you liked this post, and stay tuned for more!

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References

1. Choong, C. Y., 2005. Dive! Dive! Dive! Oviposition behaviour of Euphaea impar. Malaysian Naturalist, 59(1): 46–48.
2. Davison, G. W. H, P. K. L. Ng & H. C. Ho (eds.), 2008. The Singapore Red Data Book: Threatened Plants and Animals of Singapore. 2nd Edition. The Nature Society (Singapore), Singapore. Pp. 247–249.
3. Wasscher, M. T., & Dumont, H. J., 2013. Life and work of Michel Edmond de Selys Longchamps (1813–1900), the founder of odonatology. Odonatologica, 42, 369–402. Retrieved from http://www.brachytron.nl/Nieuw/Wasscher%20&%20Dumont%202013%20Selys%20Odonatologica.pdf

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