The Tawny Mime (Papilio agestor Gray, 1831) is a tropical papilionid butterfly with a wide distribution, from Pakistan across northern India, Nepal and Bhutan and down through Myanmar into south-east Asia as far as peninsular Malaysia. It is usually found in hilly areas, between 1200 and 2500 m, such as the foothills of the Himalayas. I took these photographs in Arunachul Pradesh, northeast India, close to the border with Bhutan.
The Tawny Mime is notable as a mimic of the Himalayan Chestnut Tiger (Parantica sita sita), which of course, it closely resembles. Despite the similarity however, these two species are in completely different families: Papilio agestor is a papilionid butterfly, whereas Parantica sita is a danaid butterfly. This type of mimicry – where palatable (or edible) species mimic a poisonous (or inedible) one – has been known about for a long time, and was named after Henry Walter Bates who discovered it in South America (Batesian mimicry). Indeed, Bate’s friend – and the co-discoverer, with Charles Darwin, of the Theory of Evolution by Natural Selection – Alfred Russel Wallace, mentioned Papilio agestor in an 1867 paper on mimicry (2).
When a species such as Parantica sita has evolved a successful way of avoiding being eaten (for example, by producing chemicals which make it poisonous or disgusting to birds and other animals!), there will be an evolutionary advantage in looking like this butterfly. So, P. sita is the model, and P. agestor is the mimic (or copier). The closer it looks like the model, the better it is protected from predators. But if the mimic becomes too common – and swamps the model – then predators with start to realise that it is not poisonous after all (!), and the evolutionary see-saw will swing back in favour of the real (inedible) species.
Remarkably there are a number of other species which closely resemble the successful model (Parantica sita) in different parts of its range: including Aldania imitans, a nymphalid butterfly only found in the Yunnan province of China; Hestina nama, another nymphalid butterfly found in South Asia; and Cyclosia notabilis (Zygaenidae), a type of day-flying moth (!), from Laos (3). Interestingly, many of these mimetic species are relatively rare, for the reason mentioned above, and so are collected by ‘butterfly’ collectors, and are available for sale on-line. I am not condoning this collecting! Better to stick to photographs in my opinion.
There are two subspecies in India: (i) Papilio agestor agestor Gray, 1831 – the Nepalese Tawny Mime and (ii) Papilio agestor govindra Moore, 1864 – the West Himalayan Tawny Mime (1). This butterfly is sometimes called Chilasa agestor agestor although other authors consider Chilasa a subspecies so use the Genus Papillio. Tawny mimes like mud-puddling; not splashing about in mud, but sucking up essential salts!
1) Anonymous. 2014. Papilio agestor Gray, 1831 – Tawny Mime. In K. Kunte, S. Kalesh & U. Kodandaramaiah (eds.). Butterflies of India, v. 2.00. Indian Foundation for Butterflies. http://www.ifoundbutterflies.org/sp/600/Papilio-agestor
2) Alfred Russel Wallace (1867) Mimicry, and Other Protective Resemblances Among Animals.