I just saw a Narrow- banded Bluebottle butterfly!!!
The rains have started in Vithura, Kerala. Even though I find the weather is more tolerable now, it is becoming very tricky to birdwatch during the evenings. Also, my friends have been warning me that leeches will become more common. I am sure I can pluck up the courage and go to the forests when hoards of leeches await my doom. Or to paraphrase Shakespeare “Love is heavy and light, bright and dark, hot and cold, sick and healthy, asleep and awake, getting bitten by blood thirsty leeches while birding and being okay with it- its everything except what it is! " Okay, I will stop being melodramatic now (maybe for a while)!
The reason I am ten-bottles-of-nutella sugar rush level excited today is because I saw a Narrow-banded Bluebottle butterfly aka. Graphium teredon drinking on the ground. Just look at him!! Isn't he the most beautiful thing that you have every seen?
How do you identify a Narrow-banded Bluebottle?
Until recently, the Narrow-banded Bluebottle, was treated as a subspecies of the Common Bluebottle. The wings of Bluebottles have brightly coloured blue-green bands contrasted by brown/black borders on both the sides, but as the name suggests, the Narrow-banded Bluebottles have narrower bands. Studies done on the Common Bluebottle show that the green colour is produced by pigments in the cells in the wing membrane (not the scales) namely, the bile pigment sarpedobilin and the carotenoid lutein. The scales at the ventral side of the wings are unpigmented and can be classified into two types: white scales and glass scales. The glass scales enhance the green colour of the band and act as polarised light reflectors which could potentially be inter-specific signals (Stavega et al. 2010).
Where are they found?
Common Bluebottles are found all over South East Asia and eastern parts of Australia, but Narrow-banded Bluebottles are endemic to Western Ghats. They occupy evergreen and semi evergreen forests and spend most of the time in the canopy of tall trees. However, they come down to the ground to mud sometimes. Here is the video of the Narrow-banded Bluebottles, slurping water from the ground.
What's so interesting about Bluebottles?
Common Bluebottles have 15 photo-receptors of distinct spectral sensitivities which can be divided into six classes: ultraviolet, violet, blue, blue–green, green, and red(Chen et al. 2016). That's completely bonkers!! Ancestral butterfly eyes had only three classes of receptors: uv, blue and green. Photo-receptor expansions happened in several species and Common Bluebottles are one of them. To give you a rough idea about how many photo-receptor types other animals have:
1. Bumble Bees, Flies: 3 (uv,blue and green)
2. Mantis Shrimp: 12-16(studies have shown that despite having so many receptor types, they cannot discriminate colours properly)
3. Common White Butterfly: 6 (uv, violet, blue, green, red, and dark red)
Given the phylogenetic closeness, I would assume the Narrow-banded Bluebottle to have similar repertoire of photo receptors. But, we obviously need to test them out empirically.
I also found an interesting study on how illumination and brightness of the pupation site affects pupal colour in the Common Bluebottle (Hiraga, 2007). In complete darkness, the larvae grew into yellowish green pupae. When lighting was of sufficient, the larvae became bright yellowish green pupae on background and reddish brown pupae on black background. They probably evolved this light sensitive mechanism to become more inconspicuous, which obviously has fitness effects.
To be honest, I consider myself lucky to be able to see and learn about the amazing biodiversity around us. All one has to do is look.
1.Kunte, K., and Gadgil, M. (2000). India, a lifescape: butterflies of Peninsular India (Hyderabad : [S.l.]: Universities Press ; Distributed by Orient Longman).
2. Stavenga, D.G., Giraldo, M.A., and Leertouwer, H.L. (2010). Butterfly wing colors: glass scales of Graphium sarpedon cause polarized iridescence and enhance blue/green pigment coloration of the wing membrane. Journal of Experimental Biology 213, 1731–1739.
3. Chen, P.-J., Awata, H., Matsushita, A., Yang, E.-C., and Arikawa, K. (2016). Extreme Spectral Richness in the Eye of the Common Bluebottle Butterfly, Graphium sarpedon. Frontiers in Ecology and Evolution 4.
4.Hiraga, S. (2005). Two different sensory mechanisms for the control of pupal protective coloration in butterflies. Journal of Insect Physiology 51, 1033–1040.