Raindrops on dragonfly wings

Sitting on a balcony in the rain with my camera, I saw a Wandering glider (Pantala flavescens, also Globe skimmer) sheltering under palms. Tiny drops flecked its wings. From the beading of the drops it seems that the wings are water repellent. I’ve seen them before in this season. Their numbers usually peak now, between September and October. They are the commonest of dragonflies in the parts of the world where most human live (which are all the places in the world where the temperature never falls below 20 Celsius). But they are uncommon travellers, as I was told recently (by Kim Smith).

Apparently they migrate between India and eastern Africa. It is believed that around the end of October these 5 cm long dragonflies will begin to journey across the Indian Ocean. On their way to Africa they will mass the Maldives. They are usually visible in the Maldives around November, and their numbers drop off by the end of December. Another peak in their population in the Maldives is in May. These peaks are correlated with the trade winds (monsoon). A clincher to the theory of their cross-oceanic migration would be direct observation, of course. But even if there were peaks in their abundance in Africa in January, or in India in June, it would be corroborating evidence. Since there is no evidence of this kind, this long-distance migration remains a hypothesis, although one with strong support. Perhaps the numbers which make landfall after the migration is small, and are replenished by breeding. There seem to be mysteries behind even the most common observations.

Resting red

Dragonflies could be seen in large numbers at the beginning of October, just after the rains. I’ve been meaning to start identifying them, so when I spotted this in Bhandup pumping station, I took photos from two different angles. It was good that I did that, because I found that the colours of the body, wing, and eyes are needed to complete an identification.

Scarlet skimmers (Crocothemis servilia, aka ruddy marsh skimmers) are common across Asia and are found, as its name suggests, in wet lands. Dredging many websites I found the perfect tool: Subramaniam’s field guide published by the Indian Academy of Sciences. This was a perfect fit: blood red face and eyes, shading to purple at the sides, blood red thorax, reddish hue on the legs. The colour of the thorax told me this was a male; females are paler, and shade towards an yellow. In confirmation of the ID, the wings were transparent, with an amber-red base, and the wing-spot was brown.

I’m glad I made a start; reading descriptions in a field guide also tell you what to look for in future. I should have taken a shot from above, to see more clearly the dark stripe which ran along its back. That identifies it as belonging to the subspecies C. servilia servilia. Its lack would have told me that the dragonfly belonged to a different subspecies, identified only forty years ago.