Morph

The common Evening Brown (Melanitis leda) is an unusual butterfly. It flies at night, and unlike many of its brightly coloured cousins, it is a shabby brown in colour. One of the first things I found about it was that it comes in two morphs. The dry season morph is really the winter morph, since it lasts from about November to about the end of April. The rest of the year you can see it in the wet season morph.

Through September and October, the end of the monsoon, I’d seen individuals which had strayed into our home, fluttering all evening around lights, and then resting quietly in the mornings. They still had their wet form, characterized by the large eye spots. There is a correlation between appearance and behaviour. These large dots are meant to deflect the attention of predators, and that’s an useful subterfuge since its activity can attract predators. The dry season form has the vestigial eye spots, as you can see in the photos, but they are characterised by the way they blend into fallen leaves. Walking through piles of leaves, you can flush them sometimes. I’ve seen them inside the house now and then, but they usually rest unobtrusively somewhere. Camouflage and this behaviour is their defense.

The word morph had me thinking wrongly about them. It is not the individual which morphs. M. leda is not a long-lived butterfly; it takes about a month, or less, to go from an egg to a pupa, and the adult lives for about two weeks. For it the universe has only one season. The conditions which prevail during the first month of its development choose the colours of the adult. Since environment plays such a big role in its development, you may wonder how much variation there is in colour from one individual to another. I haven’t noticed much variation in the wet season form (maybe I’m distracted by the eye spots), but going through my past photos I discovered that the dry season form is quite variable. Apparently an enthusiast has photographed more than a sixty different variants. Diet makes the butterfly!

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