Barefoot Notes: The Fall of Specialists and the Rise of Generalists, Or, What Ails Urban Insects?

Photographing moths in the central Western Ghats. Light curtains are the best way to explore moth diversity.

Many years ago, I used to wait for moths to enter my urban home through the old casement windows, and hover over to photograph them on an incandescent light. It feels so long ago; today, those windows have changed to the sliding ones, coupled with a netted window that keeps most insects out – even when it is open, the only ones to sneak in are mosquitoes all year round. Moths that would visit were of various sizes and colours. Mind you, my house is in the middle of one of the most densely populated cities in India. Seeing any insect here was allowed due to proximity to the remnant copse comprising of mangroves, gardens and urban farms – and, perhaps more so, vegetable wholesale markets – more on the latter in a while.

Moths from years ago: Top Underwings: Thyas coronata and Achaea janata;
Bottom Hawkmoths: Theretra alecto and Agrius convolvuli.

From the Underwings to Hawkmoths, my nights during summer holidays were about reading and checking the porch and window lights at short intervals. I would leave windows ajar to let all insects and spiders in. Sometimes, a pleasant visit would be by a praying mantis, mostly the Asian Giant Mantis who would spend a few hours till I let it out to find its own kin. At other times, the Ladybird beetles would visit – mostly the Six-spotted Zigzag Ladybird – who would be promptly let out as well. Moths, however, always dominated. Over months, I would wait for that one colourful moth over a visit among the browns, it would usually be an Underwing, rarely a Convolvulus or Oleander Hawkmoth. Such nights were a win. For me, their haven was mostly the adjoining copse. This was at a time when internet was a budding source of identifications for the popular group of insects. Most of the early guides published were from North America and Europe. Among Yahoo and Google Groups for the more popular butterflies and dragonflies that I was already drawn to, photo-hosting platforms such as Flickr, run by moth experts, is where I started documenting moths from my hometown. Eventually, the picture became more and more clear. I was to discover that there is more to these urban insects than meets the eye.

You see, their presence was not entirely of causes associated with wilderness in the strict sense, save those that belonged to the remnant natural spaces, such as those along rivulets and lakes, in the city. It was because of the surrounding country farms, large wholesale vegetable markets, and gardens and urban farms that could sustain several species. Most were pestiferous in nature – they fed on vegetables grown for human consumption, and only few eked out a living naturally on rooted plants within the city. I traded my weekends for trekking and exploring the western ghats to my east and the Konkan wilderness to the west. Here I met many more moths and other insects and reptiles and birds, and my virtual collection grew. Doing this, I realised a distinction in moths from the city and from wilderness areas far from the city. Clearly, both showed distinct populations with little overlaps. Moths in wilderness areas showed higher species diversity than the city, no doubt, but they also indicated why this is so – quite obviously, the wilderness moths are more diverse because of more plants – their larval host plants – make up natural spaces than city spaces. I believe my theory made sense, albeit without empirical evidence. Turns out, almost all the moths at my home were some or the other kind of pests on vegetables grown for human consumption. They comprised a larger part of the urban biodiversity in the heart of the city – not on outskirts, nor in a less-developed area with remnant forests and open spaces. Farmlands showed a mix of both, wilderness moths and pest species, but in varying proportions. Eventually, I found this link with the beetles too, and gradually with ants.

A feast of urban moths: Pygospila tyres (bottom) and Anomis flava (top), along with two Erebid moths, feeding on Lantana camara flowers late in the night.

This made me wonder, when we celebrate urban biodiversity, what exactly are we cherishing? How do we know who ekes out a living and who thrives? Where are they in the city – the ever growing periphery consuming more wild and farm lands, or the urban concrete jungle? Who is the last species or generation of a densely human-populated part of a metropolis? And finally, what is the proportion of non-pest and pest insects in this habitat? I believe the pest ones thrive in terms of species diversity and abundance, the non-pest barely – and they both represent urban biodiversity. I could never put this to test. Eventually, I moved to a wilderness area and became used to wilderness, often non-pest, moths. Over the years, my hometown went through a dramatic change.

A Google Earth snapshot (2000 to 2021) of urbanization in my hometown.

In the first two decades of this century, as I was engrossed exploring insects of the countryside, a rapid change was taking place all around my home. Old copse, plantations, and mangroves were being razed or buried in debris to build newer homes. My apartment complex, too, was once a marshy part of a small rivulet, now turned to a sewage canal. The leftover marsh and lakes around were reclaimed – as is the term used for urban development – throughout my childhood. Mantises stopped visiting, as did Ladybird beetles. Moths returned once in a while. Today, there are hardly any visitors at all, only uninvited guests – the mosquitoes, as the city sees a rise in malaria and dengue. I left behind this concrete jungle early in the previous decade. In the wild, moths were everywhere, I set out light canvas to attract them, and submerged into this sea of moths big and small, black as coal to rainbow-hued. I was delighted to be surrounded by so many as much as I feel ashamed now to admit that for long I forgot about my urban moths. Back home, they were disappearing even as I was relishing in the company of their distant wild kin.

Two of the most common urban moths to be encountered in India.
Diaphania indica and Spoladea recurvalis.

Moving back to a small city – in the heart of it – I found the company of urban moths as I did as a young explorer. Here, in a dusty central Indian city, they visited my apartment in all seasons. I was thrilled. Only that my stay was short-lived. Eventually, I realised that most moths were not from nearby forests (there wasn’t any close by), but urban vegetable gardens and bramble along Arpa River. Indeed, these were mostly pestiferous in nature – moths on cereal, grain, vegetables and fruits… that they comprised a large proportion of urban diversity was not surprising. In the larger discussion around urban biodiversity, we seem to have disregarded what comprises this diversity, and why it matters when we clump them all as biodiversity.

Two of the wild moths, not uncommon in forest areas, from India.
Trypanophora semihyalina and Artona sp.

It is not solely about native versus invasive species. As an ecologist, I have come to realise that they all play a part in an ecosystem. In such an altered and disturbed environment, invasives fit for survival – the generalists – do outcompete native – specialist – species, but in the given context of an altered ecosystem where specialist habitats itself are rare, invasives are not all bad, it is the management of invasives that is bad, as much as it is the protection of the native that is often disregarded in the face of development. When it comes to pest species, both, native and invasive, can be equally damaging, whether to natural standing vegetation or farms. This, is about knowing who calls urban ecosystem home. When I say there are more pestiferous moths in my hometown or my workplace, it is not to belittle the hardy species that are fittest to survive this unforgiving ecosystem. It is to give them space in the umbrella term of urban biodiversity. Moths of spinach, carrots, cucurbitis and fruit-piercing moths that stalk fruit lorries, are all to be appreciated as much as the native sunbirds, tailorbirds, and sparrows. It is important to know and acknowledge their presence.

But it is also a reason of caution: What if most cities are now dominated by such hardy, often pestiferous, species? What does that say about urban biodiversity? The thing is, we don’t know, I present only a rough idea. It is only anecdotally known that urban bees, butterflies, and non-pest flies are disappearing (and replaced) from urban ecosystems; at what pace, by what rate, remains unknown. We Indians don’t know what is happening to insects in the most easily accessible of an ecosystem, what are we to know about the wilder species declines?

Out of nostalgia, but also for something more pressing, I dig into my memory to reach those simpler days of finding moths in the middle of the city. I wish we didn’t have to do this. The more pressing issue is that there are no long-term insect monitoring projects in India. A few exist by moth hobbyists who have been putting up curtains in the same locale for years, such as to celebrate Moth Week, by opportunistic photographers like me, and by insect samplers which are increasingly rare, but these are not collective in approaches. All India has of its past – a decade or more ago – are samples in vaults that a researcher cannot ordinarily access and record. It is time to digitize this database so that biogeographic and diversity related historical studies can be made accessible to foresee what’s to come.

Moths enjoy visiting flowers in the day as well. Planting native flora (such as this Senecio grahamii aster being visited by Amata sp.) and shrubs (such as this Lea indica being visited by a Sesiid moth), are a boon for urban adult moths.

For urban biodiversity-seekers, it is important to see the big picture. Today’s cities need no gardens or Miyawaki forests, it needs native micro sanctuaries – brambles and seasonal grasses and slow-growing herbs shrubs trees. Merely seeking solutions to carbon emission has further destroyed India’s understanding of a natural space or wilderness, right from government officials to urban researchers, everyone is blindsided by the quest to sequester carbon, putting biodiversity in peril. Ideas such as nature-based solutions are considered as far-off places where wild elephants and tigers roam. It is natural spaces, made up of naturally grown indigenous plants with regular upkeep to remove invasive flora, that strengthens native species diversity and fights climate change.

Over the years, shuffling between moths far from urban areas and those from urban, I noticed a trend. Beyond the native versus invasive species debate, with due credit to the invasives that are indeed a part of biodiversity in the Anthropocene, no matter what one says, I wondered what is more intrinsic to diversities of moths in these two habitats. Is there anything at all beyond species count? I believe there is.

Twenty of the common species of non-urban and urban moths, mostly from Central India.

Between the two moth communities, I noticed the urban ones to be often dull and drab in colour, but I wasn’t so sure. I decided to put this to test: I selected ten moths each common to non-urban and urban ecosystems that I have encountered over the years in Central India, and created a colour profile using Adobe Color, a free Adobe™ online software that allows one to extract colours from a photograph. Taking snapshots of the thorax, abdomen, wing shoulder, mid-wing, and wing-tip, I created a five-point colour theme for these moths. Of course, my method is crude – I did not correct for exposure, calibrate colour, nor segregate flash photos from natural-light photos, neither did I use a robust method to select these moths. Nonetheless, there was something to be seen.

A moth palette: The moths with their distinct, major colour compositions, grouped for common non-urban and urban moths, show a perceptible distinction: non-urban moths are often with bright, contrasting shades, urban moths are often dull/drab in colour - this, at least, is the hypothesis.

The result seem to indicate what I theorize – urban diversity, symbolised by moths, is largely dull or plain. In other words, urban moths are usually less brightly coloured or aposematic than their wilder counterparts. This is nothing unusual, most pestiferous insects are dull/drab in colour to blend with the environment. This is not to say that there are no dull/drab moths in non-urban ecosystems, there are many. What is important is that as urbanization increases, urban insect biodiversity is represented more by dull-coloured species (with exceptions) than the non-urban. Of course, this needs better testing, and I speak only of moths. Urban areas with plentiful green spaces might not stand this test.

The fading colours of urban biodiversity should ring alarm bells. Just as trees are being cut, rivers smothered, and forests making way for concrete jungles, specialist insects are disappearing or are being replaced by generalists – mosquitoes such as Aedes, Anopheles and Culex are more common than hoverflies, soldierflies, and robberflies. Butterflies replaced by moths that eke out a living hidden away in leftover vegetables. Mormons, Sailers, Bluebottles, Evening Browns and even Grass Yellows have fast disappeared from my hometown, replaced by Cutworm, Bagworm, Caseworm, Stemborer moths.

An otherwise beautiful view of the Satpuda in Melghat is dominated by 'brown' teak trees, affected by the Teak Skeletonizer moth that chews up green leaf and leaves behind the skeleton, a natural outbreak fairly easily resisted by natural forests such as in Melghat Tiger Reserve.

Last week, I found myself up in the highlands of Central India, by the Sipna River of Melghat Tiger Reserve. Even as I was musing the idea of differences in colourations between non-urban and urban moths, I was talking about insects of a protected area, dominated not by colourful moths as I predicted, but by a dull/drab pestiferous moth, the Teak Skeletonizer, that was the most common in the forests and at porch light. This well-known moth skeletonizes green leaves by eating the non-veiny part of the leaf, leaving behind a leaf-skeleton. Does that mean that my theory is incorrect? No. Skeletonizer outbreaks are climate-dependent phenomenon, and are not always the most dominant in all years. This year, I was told, happened to be an exception when hundreds of teak trees were skeletonized by their caterpillars, painting an otherwise green mountain-scape a drab brown, as if it is summer.

A swarm of Small Mayflies around a porch light by the bank of Sipna River.

Yet, the insects showed their force in numbers. On the day of my arrival, the long August dry spell broke, and rain resumed over much of Melghat mountains. That night, millions (no exaggeration) of mayflies and non-biting midges emerged from Sipna River, as its water gradually swelled with fresh rain. They shrouded all lights at the camp, making it difficult to walk by the porch light, yet it was delightful to be amidst their swarms. This continued for two nights. During this time, there were very few moths around – this is because August in central India is a time of caterpillars; it is in the early and late monsoon that we can see a large diversity of adult moths. In a corner of the canteen, we were witnessing Central India’s first Dobsonfly, Nevromus intumus, a Himalayan species. Apparently, this is major range expansion for this species, a rather rare insects whose aquatic larvae spend years in unpolluted flowing mountain rivers.

After talking about insects and being amidst large swarming mayflies, I was back at Amravati. The weather was pleasant, rains had lashed the city in the plains as well. However, scarcely any insects flew around lights in the city, even along the outskirts. There were no moths, no mayflies, just a handful flies. This stark contrast was not solely because of habitats – mountains versus plains, it alluded to the dwindling insects in urban ecosystems. Ironically, I deduce this in an already altered habitat – porch lights by a wild river and incandescent lights by city streets, both altering insect assemblages because of artificial lighting.

This is how natural spaces are reclaimed, and biodiversity rechristened as
'urban biodiversity' a blatant exploitation of nature for 'views' - an example of Green Washing.

This is not a celebration of urban biodiversity, this is a lamentation. Every day, we inch farther from understanding how and why and at what speed insects are declining in India, especially cities, even as cities encroach upon wilderness and revel in labelling displacing wildlife as urban biodiversity. Without academic nor institutional support, urban insects remain one of the most underappreciated and understudied part of biodiversity. It is true what one has said, a known devil is better than an unknown devil – maybe we understand cities too well as harbingers of destruction, a sure-shot way to extinction, than, say, climate change which we race to try to understand better. Maybe urban insects are already doomed, and it starts with specialists disappearing and colours fading. Maybe, and I hope this is more correct, I am wrong in this assumption, but truth be told, we are ignorant of the fact that there are significant changes happening around us.