The Mithun and the Fly: Memento vivere, memento mori

The skull of the Mithun (Ward, R., 1903) and the Piophilid fly (Curtis, P., 1826)

In the Nyishi culture, the significance of Mithun, Bos frontalis, as the sacred animal, is crucial in death as in life. It is the crux of social prestige where the animal is gifted by the groom to the bride’s family as a marriage custom, and no major ritual or ceremony is complete without an offering of the Mithun. A sacrificial animal that represents the spirit of culture and nature, they are semi-domesticated and unlike cattle. Their behaviour of spending time in the forests away from villages is akin to their cousin the Gaur, Bos gaurus, their owners seldom if ever see them. A large bovid of the Eastern Himalaya, its presence is calming. In the foothills, the trails through the dense forests are likely made by the Mithun – trails leading away from villages in the valleys mostly start as such. On a trek up the mountains, a Mithun would follow you out of curiosity or pointedly look at you walk by. Despite having ownership, it is not surprising to find a herd of Mithun deep in the forests where people seldom go.

A Mithun looking on at passersby

When seeing the Mithun for the first time, their appearance seems dreamlike. Whether due to the lush ecosystem they are a part of or their demeanour, or both, it takes no second look to guess that the life of a Mithun is blurred by the real and ethereal – between this world and the world beyond. For the uninitiated in the world of tribal culture, this duality of life is important to understand and acknowledge.

In life, a Mithun’s value is not merely transactional. Beyond the social prestige, it symbolises self-reliance and a connection that is seldom, if ever, seen in urban India: that string that keeps one attached to nature. The nature of Mithun is as tame as it’s connection with humans and as mysterious as the wild. A Mithun walking through the forest creates paths for humans to follow into this unknown, to learn of it. As browsers, they consume fruits, leaves, and grass, aiding in dispersal of seeds and mixing up the tree communities as they move between elevations. And like any large herbivore, they are efficient biomass converters, their dung nourishing the soils. Ants, flies, and beetles, home-in on this resource, feeding and aiding in its decomposition, quickening nutrient turnover – an overlooked factor in biodiverse regions. And as mammals, they become prey to the predators of the wild – the dhole and the tiger – while this draws the ire of the owners, a Mithun is as integrated into its ecosystem as it is a part of human culture.

In death, the Mithun appeases the Gods and protects the humans. The wrath of the Gods may bring ill-fortune or ill-health upon the entire village, and a sacrifice of the Mithun serves as the ultimate ritual – there’s nothing that cannot be unmade after a Mithun’s sacrifice. A feast, a custom that marks the event, is celebrated in respect of the sacrifice made for the Gods. The most well-known is Nyokum. An important festival, it is not merely a celebration but a custom of caution. Conducted in the month of February, the appeasement of Gods for a good harvest and good health is led by sacrificing the Mithun, carefully selected and prayed to, and its flesh consumed in reverence. The Mithun connects the life with the afterlife – it is not about idols or images, it is about earth, river, rain, nature, wildlife – and the hazards associated with them: earthquake, flood, drought, predation, that may befall a village.

A Mithun passing through a community forest in the east Himalayan foothills

The Mithun empowers humans, who regard its flesh holy. Every part is consumed, prepared with a skill honed over generations – as ancient as when the Mithun was first associated with humans roughly 8,000 years ago. For a one-ton animal, skin and bones are a major organ left behind. The hide may be used to create leather. The skulls may be hung from the walls – a mount of the Mithun is symbolised on state emblem of Arunachal Pradesh in a similar fashion. The sharper bones may be shaped into tools. And the rest returns to the forest. There are no ‘discards’ unless there is an excess of bones.

On the forest floor, the concept of ‘waste’ – something that is of no human-use – has no meaning. As the Mithun’s purpose connecting humans with the supernatural continues in its afterlife, its purpose in the lap of nature continues in this world. The leftover muscles, the cartilage, the fats, nourish the forests. The beetles scavenge on these sacrificial leftovers, the ants carry them back to their colony. Sometimes, butterflies and moths feed on the calcium-rich bones and deer and the canids nibble on them. The flies and the beetles complete their entire lifecycles on this resource until only calcium is left. In death, an animal is as with nature as in life. It’s role – as humankind defines for anything living – is not ended. Its ‘function’ continues, invisible to us, beyond our ecological understanding, which is identified, as a symbol, in tribal cultures.

A Mithun skull (upside down)

Peering into dead and the decaying is as much an ecological curiosity as it is philosophical. In 1995, far from Arunachal Pradesh, one Russel Bonduriansky peered into the shed antlers of moose in Algonquin Provincial Park in Canada. Tiny flies caught his attention. He was to find that these were flies new to science – small 2-4 mm adults that lived their entire lives on shed antlers – aptly calling them Antler Flies. It was an observation rarely made in the wild – the ‘role’ and the ‘function’ of animals long after they have passed away, or, in this case, having shed an organ.

Dr Bonduriansky aptly assigned them the scientific name Protopiophila litigata – a primitive relative of the cheese-skipper fly, Piophila, that was associated with cheese-making infestation in Europe, Piophila itself meaning fat (pion)-loving. The ‘skipping’ refers to the behaviour of the maggots – fly larvae – to spring-off its food source. Litigata means ‘to fight’ or ‘to contest’, also the root of the English word ‘litigate’. He had a good reason for this. The flies were not mere egg-layers, they sparred, much like the moose that had shed his antlers did, to claim a territory – a portion on the antler – and to win over a mate. Dr Bonduriansky found the males using forelegs – much like moose antlers – to contest one another, as females that were larger than males observing. Once the female accepted the male, she allowed him to piggy-back her, and they found an oviposition site on the antler to lay an egg into the pores even as the male warded off rival males. This elaborate behaviour was starkly different than for a related species, Protopiophila latipes, a species well-known in forensic entomology to estimate postmortem interval through their lifecycle. Dr Bonduriansky observed that ‘mate guarding’ was not observed among these flies, and they preferred flesh and bones such as skull than antlers.

Many years later, I read about the antler fly in a book by the Canadian dipterist Dr Stephen A Marshall, with whom I’ve had an opportunity to interact briefly over email. I consumed the massive volume as I worked on the manuscript of the Diptera (Flies) of Mumbai and came across the antler flies that held my fascination for over a decade. The idea that there is no resource that a fly wont exploit – not in an abusive sense – rang true when I read about them. Here is a fly that utilized the rarest resource – the tissue within the pores of bones and evolved an intricate way to fight for and win over a partner to utilize this resource. The Piophilidae – a small family of about a hundred known species – is mainly known for its members feeding on carrion, but some are pests on meats and cheese, some are parasitic in bird nests. Some carrion feeders are useful to determine the time of death, especially for human deaths under uncertain circumstances, and very few of these specialise on bones, all in the subfamily Piophilinae, called bone-skippers. The antler flies, and generally the bone-skippers, became my obsession.

My opportunities to look for them had me peering at bones whenever I travelled extensively to forests. Chances of finding antlers were rare. Indeed, when Dr Chris Angell who did pioneering work on senescence among antler flies – a first among wild invertebrates – was asked ‘How far do you have to hike in the woods to find a moose antler?’ He remarked: ‘A long way, let me tell you.’ The antlers of chital and sambar I searched for were mostly old and dry – not an ideal place for antler flies.

New Oriental Sepsinae. Brunetti, E., 1909

For a small family such as this, its representation in India is further small. Only four species are known to modern India, all of them due to their role in forensic entomology as insects that lay eggs on cadavers, all of them found along the Himalayan foothills, from Kashmir to the northern West Bengal. Brunetti identified one in 1909 as Piophila ruficornis var. flavifacies, which was Piophila casei – the cheese-skipper fly, from Kurseong. Dr Marshall mentions one ‘Centrophlebomyia anthropophaga’ from a dead horse in Kashmir – it has not been recorded since. It is likely that Piophilids who specialised on bones were not found in Central India. Even as I explored flies opportunistically, I pushed them to the back of my mind.

Scavenger flies (Sepsidae) on a leaf next to the Mithun remains. A typical indication of animal matter about.

A decade later, I found myself peering into the skulls of Mithun on a dry stream bed, possibly flown down after the Nyokum celebration, in the Papum Pare district. Hundreds of Sepsids – the Scavenger Fly – swarmed the sacred remains, with a faint but distinct rotten smell indicating leftover tissues as a resource. Larvae of Stratiomyidae (Soldier Fly) fed deep inside skulls, those of Psychodidae (Drain Fly) and Culicidae (Mosquitoes) fed in rainwater collected within them. As I peered over, I remarked to my friend, if only we could find that fly here – him being clueless to what I was muttering about. The skull was swarming with tiny black flies which were similar to Sepsids, and I finally sat by the skull to look closely.

A rare landscape on a niche habitat

The flies were concentrated on the horns, and scuttled around in a random fashion. Only when I settled by did I realise that I was possibly looking at Piophilids, something resembling the behaviour of the antler flies: some flies held out their forelegs and displayed their wings sideways, much like the antlers of a deer, to spar – these were the males who ‘pushed’ one another back and forth, often in multiples of three or four, instead of the traditional two. Some larger individuals with a pointed abdomen – the females – wandered about, trying to find a way around the frenzy of the males.

Scuttling about to spar

The whole of this was unfolding on both the horns, not more than ten inches in length. It was an entire landscape of its own – a crucial aspect of the lives of these flies. The cornual process was fully exposed, and the ‘horn’ – the keratinous layer – had been eroded. The cornual process – the living bony structure, was entirely porous, like a maze that went deep inside the cornual diverticulum. Between these pores were funnel-shaped openings of arteries and veins and nerves. A bovid horn is unlike a deer’s antler. Horns are permanent and are ‘alive’ – they are not mere keratinized structures but feel and are sensitive. Antlers reach a stage where the organ is cutoff from the circular system and fall off at the end of the breeding season and thus differ structurally from horns. Finding a dead horn is therefore finding a dead animal – it is intact with the skull.

A couple of males trying to ward off a male guarding a female as she inserts the ovipositor in the bone structure

Still muttering to myself this is likely them, I found a pair of flies in the copulation position, and followed them. Several males still tried to fight-off the piggy-backing male, the female – much larger – carrying him, used her forelegs to ‘feel’ the pores, and whenever they weren’t pestered, she inserted her ovipositor in the marrow, possibly to feel or lay an egg. In the small time I spent with them I did not see them actually copulate. Dr Marshall’s succinct description was enough to bring my hopes up, but mere behaviour isn’t enough to tell a fly from a fly. Possibly at my friend’s end of patience, I tried to photograph a pose in which I could see the fly’s wing that would take me one step closer to confirm.

The June of the foothills is sultry. Hot and humid, but green and blue, it is the most ideal time for insects to be about. Drenched and heaving, I finally got up, only to see my friend move farther ahead, and called the supposed ‘antler flies’ of India a goodbye.

A preliminary search boosted my confidence in the identification, but it was Dr Chris Angell who further confirmed that it belonged to the genus Protopiophila – a relative of the antler flies indeed. He tentatively identified it as Protopiophila contecta, a Southeast Asian species, based on some morphological keys such as a distinct grey line on anepisternum, and provided necessary literature to piece it together.

A female ovipositing in a hollow - possibly an arterial opening, as another watches on

That I found a fly that specialised on bones I had always pondered would be here in India, was found feeding on the remains of a sacrificial animal, made this a special occasion. That I found a fly that is possibly a first for India, made me realise how ignorant we are – at least I am – of our own understanding of ecology. Besides being a largely ignored group of biodiversity, in death live specialists that are linked to a thousand-year-old tradition. The flies, if I were to extrapolate from observations from Algonquin in Canada, would complete their lifecycle over the period of monsoon, their larvae possibly wintering in the pores of the horns itself, emerging the next summer.

The male warding off a rival using its wings

I wonder how they find other sources of horns to spar and mate and lay eggs, it’s not a common resource. Studies from South Korea, where the species was recorded for the first time in 2026, indicate P. contecta to be opportune in nature (Han et al. 2026. Doi: https://doi.org/10.1111/1556-4029.70383). Adults were found on a ‘large, rotting heap of mixed food waste’ of a commercial restaurant on the edge of a forest. In 2015, P. contecta larva were found on human cadavers – specifically in bone marrow – in Japan (Kirinoki et al., 2015. Doi: https://doi.org/10.1016/j.forsciint.2014.12.026). If anything, the Asian bone-skipper fly, as I like to call it, is a generalist, but shares the same behaviour and affinity to horns like the antler fly.

While Holarctic in distribution, some Piophilids have a Palearctic distribution with the Himalayan foothills forming the southern-most boundary in South Asia. This region is a tropical forest bordering the temperate Himalayan forests, which is where most of India’s Piophilid records come from. It is likely that there are more Piophilids as one goes further up the Himalaya. It is therefore more than a mere encounter to find them at the edge of their generally established distribution range.

A Scavenger Fly (Sepsidae) backs off as a pair of Asian bone-skipper flies ward off rivals

The Asian bone-skipper fly might not be the ghost of the Himalaya, or the spirit of the Himalaya, what have you. It stands at the cusp of life and death – it has utilised resources we think are beyond function. Just as the Mithun enters the afterlife to make the living, in simplest terms, easy, the fly enables the Mithun’s body return to nature. At 4 mm, it stands as a reminder that in death as in life, there are those who help connect two worlds, and those who help them.