Diptera of Mumbai
Update (November 27, 2017): A detailed paper (with more pictures) has now been published. See it here.
Then near and nearer drew,
Thinking only of her brilliant eyes,
And green and purple hue-”
- Mary Howitt 1821
|A Robberfly scanning the grassland of SGNP
There are over 1000 species of plants, 251 birds, 40 species of mammals, and it is estimated that there are approximately 5000 species of insects in Sanjay Gandhi National Park, and I estimate there to be more species of insects in Mumbai and the surrounding areas. Among insects, the diversity of butterflies is very well documented in Mumbai, and is the only insect in Class Insecta that is studied so well. Then there are arachnids that are well documented, yet not comprehensively put together into one pictured guide. In all these innumerable Orders we explore, what we don’t see is other creatures living not only in forests but in the city itself. Some insects are so common that we tend to overlook them. One such not-so-beautiful creature to look for is a fly. It is not difficult to see a fly, many nature enthusiasts do, and many take pictures too. However, there is not enough information on how many flies call Mumbai their home, except for some highly specific research papers which are not easily (or freely) accessible for amateur naturalists. The knowledge of biodiversity gained through research should be available freely – especially on the internet – since I think this is the prime reason why there is such a big lacuna in the biodiversity study of Mumbai, or any other city in India. But let’s keep it aside to discuss some other time and focus on Diptera today.
Diptera is one of the 29 orders of Insecta. There are 188 families in Diptera, and the number of species is estimated to be 1 million, of which only 150,000 different kinds of flies are known to us. With such an abundant diversity, it is surprising to see no information on Diptera of Mumbai. This is partly because Diptera is not as beautiful a family as Lepidoptera. It doesn’t even sound cool. All dipterans are small compared to Lepidoptera or Coleoptera. Simply put, they are not worth noticing, and are plain ugly. I do not blame anyone for not seeing a fly but it’s not just about the looks! The major reason behind finding it unattractive is because we have learnt since childhood – flies spread diseases. If you see a fly, swat it. If you see a fly sit on your food, don’t eat it. Although this is not true for all flies, our education doesn’t say which fly is dirty – a housefly or any other fly. It only teaches us to keep away from flies. So, with all due respect to other beautiful insects out there, I bring the family of flies up from their “dirty” reputation, alongside all the other beautiful creatures of Mumbai.
I started writing this article after finishing Common Spider Families of Mumbai, but I never got around it. It has been a year since that article, and I received a good response from many naturalists in and around Mumbai. This is an article on one of the insects of Mumbai’s forests that I happened to study – and with this article, I will post some more Biodiversity of Mumbai articles in a few more years to come.
Flies. I like flies as much as they like to annoy us, and as much as we like to whack them and some love to fly away from us as much as we like to run after them for a photograph. And with flies such as houseflies to annoy us, there are other beautiful flies around, some are blood-thirsty, some flower-loving, some predatory, some parasitic, some dancers and some pests. This is enough to sum the vast diversity of Diptera in Mumbai, but if we are to study them closely – they are bizarre, alien, and unlike butterflies, lack common names (making them even more painful to identify), as is the case with most moths seen in India.
The area covered was in and around Mumbai, including the suburbs. The observations were made at Sanjay Gandhi National Park (including Yeoor Hills, Nagla Block and IIT-Mumbai areas), Tungareshwar Wildlife Sanctuary, Karnala Bird Sanctuary, Matheran ESA, Thane, Karjat, Vasai Fort, Mahuli Fort, Jijamata Udyan and Mahim Nature Park. All the flies were seen and documented on nature walks; hence the sampling was random, and done over a period of three years (2007 to 2009). Most flies documented were also photographed; however there are non-photographic records of few families.
Identifications were made solely based on photographs, therefore very few flies are completely identified up to genus, but the checklist of the families was made with help from experts via internet. This is not a comprehensive checklist, but an attempt at recording all the Diptera sightings occurring over a period of three years. This also does not give the confirmed number of families, as I must have missed several of them; some of the families are in fact beyond identification unless they are observed under a microscope. I relied mostly on journal articles and research papers from India, but no papers were available pertaining to the state of Maharashtra.
After I researched on the little known Bugs of Mumbai, I realized how few Dipterans are known to me. This is one of the most challenging orders to study, therefore it is not surprising to see scientist and taxonomists reordering and renaming them all the time. The New Diptera Site has a good deal of information on Classification of Diptera. Web-sources like this inspired me to reopen the old pictures and get them identified as fairly as possible. I do not like to keep anything unidentified, but sometimes some images get overlooked – as was a case with the Dipterans.
Describing a fly is very easy. It stands for “two-winged” creature, where a pair of forewings is used for flight, and the hind-wings are reduced, called “halteres”, which assist in flight. We all know how hard it is to swat a fly. They are one of the strongest and quickest fliers living, and behind their swiftness is a complex mechanism of balance, strong thoracic muscles and nervous coordination.
The flies mentioned here is my personal checklist of Diptera families. In all, I came across 22 confirmed families existing in Mumbai, excluding the confusing families of Midges and Gnats, and some other unconfirmed families (approximately 30 families). None of these fly families are rare, so I expect to find some more, rare and inquisitive families exclusive to Western Ghats. In fact, all the families listed here are the top 20 largest families of Diptera (Brown, 2005). Several flies are threatened by loss or degradation of habitats. The IUCN Red List includes seven species, of which three are extinct; two are listed endangered, one critically endangered and one as vulnerable. The species-at-risk flies are from United States and Australia. I am assuming there is no literature available on the internet on Indian Dipteral species-at-risk.
Understanding flies is very important to us, not merely because we must map the biodiversity – that’s not why everyone will look at flies, but because flies are the most important arthropod vectors of disease in humans and animals. They are responsible for most insect-borne diseases and deaths than any. With flies such as mosquitoes – the dreaded host for malaria and other diseases, to parasitic flies such as Blowflies and Horseflies, to pests such as Fruit flies, to flower-loving Hoverflies, supreme predatory Robber flies and thieves like the Kleptoparasitic flies – who would think that flies are merely just… flies? This behavioral diversity is not seen in Odonata or it’s not so extreme in Lepidoptera and Coleoptera.
The families seen in Mumbai are described herein, starting from the most common, to the uncommon and lastly the uncertain, confusing fly families, such as Midges, Gnats and others.
Better known as Mosquitoes, Culicidae literally means a little fly. There are about 20 genus of Culicidae in India, and several hundred species. They are the most dreaded, hated and commonest flies seen. As we are aware, only the females need to feed on a protein-rich diet of blood, for nourishing the eggs. The males feed off on plant sap, and seldom visit houses. The mosquitoes manage to find their victim by acute sense of odour, thanks to the olfactory nerves in the antennae.
|A freshly emerged Tiger Mosquito - Aedes sp.
We know where mosquitoes breed since this is the insect which has gained highest public awareness, for obvious reasons. Best way to get rid of mosquitoes is not only to remove stagnant water, but also to breed fishes. Other alternatives are having Odonates – the naiads as well as adults – in the backyard or other predatory flies such as Robber flies. These are one of the most efficient natural mosquito population controllers.
The family of House flies. I did not come across a species checklist for India, but one paper on Northeast India states 108 species in Muscidae. I cannot speculate the number for Mumbai, but the diversity in Muscidae is interesting enough to be mapped. It will help understand the harmful flies as well as the useful flies for Mumbai region.
|A Housefly in the genus Musca
If you ever associated flies with flowers, Syrphidae is a family you will mostly cherish. They come in various shapes and sizes, from tiny Hover-flies to large Syrphid flies (not all Syrphid flies are Hoverflies, because they do not hover). This family of flies is known to mimic bees and wasps. Besides sitting on flowers, the Hover-flies are commonly seen hovering midair, hence the common name. This is another common family of flies that are seen throughout the seasons, although less in numbers during winter.
|A mating pair of Hoverflies
Commonly called Blue-bottle flies or Blow flies, these shiny flies are also amongst the most common seen around. Whether it’s a rotting animal, decaying plant matter or feces, this fly will be abundant at such places to lay eggs. They are also efficient pollinators, and often visit various flowers, especially those that give out a pungent odour. These flies are also important in their larval stage, since the maggots help breakdown of the decomposing animals. The maggots are used in Maggot Therapy, since the maggots exclusively feed on dead tissue. The most common genera of this fly are Lucilia sp. (Blue-bottle fly), and Chrysomya sp. (Blowfly).
|Blowfly - Probable genus Chrysomya
|Possibly Stomorhynca sp.
Sarcophagid flies are commonly called Flesh flies, mainly because most species lay eggs in dead animals. For this reason, forensic entomologists can predict the time of the death of a person, if the body is affected by Flesh flies, since different species prefer different body organs in different states of decomposition (Source). Other species are known to lay eggs in open wounds, but I don’t think that is a problem in Mumbai. And some species are predatory on insect larvae and mollusks. I came across an interesting paper, where the researchers studied Sarcophaga misera, a species known to prey on a freshwater snail Indoplanorbis exustus, a vector of schistosomiasis. The research shows that larvae of the fly killed the snail within 15 to 60 mins. It also states that chemicals are usually used to control these snails, but if there are natural pest controllers such as these flies out there, we don’t need to pollute the environment so much! The paper can be accessed here.
|Flesh fly - Parasarcophaga sp.
The flies belonging to Asilidae are commonly called Robber flies. They are aerodynamic predatory flies, very common throughout forested areas. The common name Robber flies is probably because they are known to snatch prey off other flies, but most often, they capture their prey themselves. There are large to small Robber flies, easily identifiable by their long abdomen, laterally flattened body and “mustache” like bristles on the head. Their eyes are well developed, and legs designed to hold onto prey. Robber flies, while hunting, prefer to perch on a vantage point, from where they are able to watch clearly for approaching prey or predator. While basking, they will either sit on the leaf or on an exposed branch. Seeing these flies, which are quite common, is also an indication that the insect diversity of that area is healthy. The adults put up an interesting courtship display as males hover over the female, while attempting to copulate. There are many more complex subtle courtship displays in Asilidae. The adults lay eggs on the ground or on plants. The larvae feed on organic matter in the ground. This shows that larvae help in accelerating decomposition of dung as well as wood, and the adults help keep populations of other insects such as mosquitoes in check. These beautiful flies are everything except robbers!
|A Bee-like Robber fly
|A Robber fly feeding on an Ant
|Robber fly feeding on a Leaf hopper
Dolichopodidae is the family of Long-legged Flies. These tiny, metallic flies are the jewels of the fly world. Most species flaunt a shiny green exoskeleton, but there are other forms that come in hues of yellow to blue. They are common in urban as well as wooded areas – although I have observed their populations declining in urban areas.
These tiny flies are seen dancing from leaf to leaf, or from fruit to fruit. These tiny flies are predatory, feeding on smaller bugs. It is always a pleasure to chase these flies for photography, but what’s interesting to photograph is their courtship dance. The males rapidly move the wings up and down without actually flying. Some species exhibit ornamented wing tips, with either a white tip or black-and-white tips in some. I recommend reading the article by Zimmer et al (2003) for more information on how courtship displays evolved in relation to the other closely related-fly families.
As is true for most fly families, identifying Long-legged flies based on a photograph is almost impossible. In fact, all the flies look same to me, except of course a few obvious morphological features such as colour, length and size of legs, as well as differences in behaviour and habitats. They are however identified based on the genitalia of males. The genus Dolichopus is the most commonly occurring, with about 600 species, although I wouldn’t predict all Long-legged Flies of Mumbai to be the same.
Flies belonging to this family are commonly called Bee flies, because of their superficial resemblance to bees. This fly-in-disguise thus gets protection from this sort of mimicry, as the predators who have experienced the sting of a bee will almost certainly avoid it. Such kind of mimicry, called Batesian mimicry, is common in many insects – and is well-known in butterflies. Although Bee-flies do resemble bees, many species are not as good at mimicking bees as other families of flies such as Syrphidae are. The adults are small; often show patterns on wings, with fluffy bodies. They are undoubtedly the soft-toys of the fly world! The adults exclusively feed on nectar, thereby voluntarily helping in pollination. The larvae are predatory or parasitic of other insects. According to Wikipedia, it is the poorest known families of insects relative to its species diversity.
|One of the common Beeflies of Mumbai
Drosophila, or Fruit fly, is well known in kitchens as a nuisance and in labs for their (voluntary?) contribution to genetics. I had no picture of a Drosophila (or a similar species from this family), since they were just too common and too tiny to photograph.
|A dead Drosophila
Flies in this family are called Scuttle flies for a good reason. They look similar to Fruit flies mentioned above, and are equally common in houses. The easiest way to distinguish a Scuttle fly is, if you go after it, instead of flying, just how a Fruit fly would, they will run very quickly and then take to wings. This could be attributed to their heavily built mid- and hind-legs.
|Scuttle fly, probably Megaselia scalaris
Commonly called Drain flies, because they are more common near damp places – such as drains, or Moth flies, because of their resemblance to moths, these flies are, although small, hard to miss. They are very common, and don’t cause any nuisance. Their presence is as good as their absence. This is one reason why I never thought about photographing one, but I promise to get one – for no special reason – soon.
|A Moth fly showing fuzzy scales and moth-like antennae
Tipulidae is the family of Crane flies, which are also called daddy long-legs, although it is used for any insect or spider with extremely long, thin legs. The Crane flies probably get their names because of the same reason – their long, thin legs. Someone must have pictured these flies to resemble cranes. They are harmless flies, although people consider them to be giant mosquitoes that give a painful bite. But Crane flies do not bite – the adults feed on nectar (pollination!) and their larvae feed on mosquito larvae (biological pest control!). Yet, with all the misconception regarding their scary appearance and the belief that they bite, these flies, unsurprisingly, do not get the fame they deserve.
|A male Crane fly, Ctenophora sp.
These 11 families are most common, now we will look at the rather uncommon families. Uncommon because they are not found in abundance compared to the families above, and some are also difficult to identify.
This family is dominated by ant- and wasp-mimicking flies commonly called as Stilt-legged Flies. They are quite larger than a House fly, with a very distinctive behaviour. The Stilt-legged flies get their name from, but of course, the stilt-like legs. These flies, when at rest, move their body forward and backwards, with the constant wavy movement of the short forelegs, wearing white socks. This constant waving is probably a way to mimic wasp antennae movement – since many wasps wave their antennae as they search for prey. These flies are also distinct because one species of Stilt-legged fly is wingless. Yes, a wingless fly (irony?), found in the Australian region. This family also contains a species-at-risk in Kerguelen Islands (in the Indian Ocean). The larvae of these flies are known to feed on ginger, or live under bark of dead trees. Some adults are predatory on small insects, or are attracted to excrement and decaying fruits – as observed in Mumbai.
|A mating pair of Stilt-legged flies, possibly Rainieria sp.,
also notice short forelegs
Soldier flies are small, fast flying flies. They are usually seen sitting on leaf surfaces, and if disturbed, fly rapidly to-and-fro, and settle on a nearby leaf. These flies come in a variety of colours, with metallic green being most dominant. They are long and slender – somewhat resembling a wasp, and sit with their wings folded one on the other over the abdomen. The larvae are aquatic or terrestrial, feeding on dead and decaying matter while some are predatory.
|Soldier fly, Sargus sp.
|Probably Odontomyia sp.
Commonly known as Non-biting Midges, the Chironomids are by far most commonly occurring flies, perhaps very close to Mosquitoes. We all know what these flies are, and we all wonder if these are mosquitoes. Even Zoology students have dissected their larvae – called Chironomous larvae, or in lay-mans term – Bloodworms. Even aquarium hobbyists feed these Bloodworms to their fish. These Chironomous larvae are called Bloodworms because of their colour – they do not contain red blood. The larvae belong to several species of Non-biting Midges, many resembling mosquitoes (with absence of long mouthparts, but they don’t bite.
It is the dreaded family of deadly flies, commonly called Horseflies and Deerflies. These flies have saw-like mandibles that they pierce and saw (quite literally) to drain blood; they then happily lap up the dripping blood. The Horseflies are usually larger than Deerflies, with a very painful bite, with some species known to even pull tiny chunks of skin! I have been chased by several Horse flies at Dandeli-Anshi Tiger Reserve. We were travelling through an open jeep to studying population dynamics of ungulates. And we were being stalked by big, sturdy flying machines that could match the speed of 40 to 50 kmph for over an hour! In fact, these Horseflies (Tabanus sp.) also rested on the jeep occasionally. I was in the passenger seat, trying to get rid of these pirates – but to no avail. I haven’t been bitten by a Horsefly yet, but had an experience with Deerflies.
|A male Horsefly in the genus Tabanus
|Horsefly, Philoliche sp.
|An Orb-weaver feeding on Philoliche sp. Horsefly
|A Deerfly in the genus Haematopota
If there are flies that steal, the Milichiidae flies should rightly be called thief flies, but there is another better name that explains this family. The flies of this family are commonly called Freeloader flies, because they are “someone who exploits chances to get free stuff wherever possible”. This kind of behaviour is more correctly called Kleptoparasitism (parasitism by theft). This is a highly specialized family (like all other Diptera families) but their skill lies in thieving. As a pickpocket has developed the pick pocketing skill, several flies here have learnt how to coax ants to regurgitate, and feed on it. Other flies prefer hanging around predators (invertebrates and lizards, mostly) and feed on their hard earned food. While the adults secretly feed off other’s prey, the larvae feed on dead and decaying plant matter.
|Freeloader flies feeding on a bee caught by a Crab spider
|Probably Freeloader flies on Lemon Pansy butterfly
While Tephritidae might not be experts in capturing prey or robbing others, they are well equipped to damage fruits. Flies of this family, hence, are also called Fruit flies. They are also called Peacock flies because of their elaborate colours and wing markings. Most of these flies are larger than Drosophilidae, and show presence of ovipositors at the end of the abdomen, with which they penetrate fruits to lay eggs. This family is therefore agriculturally important because of their damage to crops (fruits), but there are also several species that prefer weeds, thus helping in destroying them.
|Melon fly, Bacterocera sp. seen at Yeoor Hills
Diopsidae is also one of my favorite families of flies. These outwardly flies are indeed alien-like compared to other flies. They are commonly called Stalk-eyed flies for an obvious reason. The males possess long stalked eyes, while females have shorter stalks, with females preferring males with long stalked eyes. During mating season, the males pump air via mouth into the stalks, thereby elongating it.
|A male Stalk-eyed Fly photographed at Kanheri Hills, SGNP
The flies are commonly called Louse flies or Keds. They are as common as there are pigeons in Mumbai. This is because the Pigeon Louse flies fall in this family. They are dorsoventrally flattened, always hiding beneath the feathers. I as a kid used to allow pigeons to nest in the balcony, and that's when I discovered these flies. Luckily, they do not prefer human blood, or at least not my blood. They are weak fliers; in fact some species have given up flying forever.
This family is very unique (yes, all are as a matter of fact), and is not hard to mistake it for a beetle to an untrained eye, and for this reason, the flies in this family are called Beetle-backed flies, or just Beetle flies. While there have been records of this family from Thane city, I am yet to stumble upon these tiny flies. The scutellum in these flies is enlarged, much like beetles and jewel-bugs, which almost covers the wings - hence it looks like a beetle, although easiest way to distinguish it from any beetle is the distinct fly-like head, fly-like stubby antennae and mouth parts.
We had a look at the families that are confirmed to be present in Mumbai, now let’s have a look at the families that may be present in Mumbai.
Flies of this family are commonly referred to as Dagger flies (because of dagger-shaped mouth parts) and also as Dance flies (although the original Dance flies belong to Hybotidae). These are mainly predatory flies, but I photographed them sipping nectar (which, some species certainly do). They are not commonly observed because they are very small, and let’s face it – many of us amateur naturalists chase big things like butterflies and scorpions. Empididae is one of the three families in the super family Empidoidea, which also includes Dolichopodidae (we already had a look at these).
|Dagger flies engaged in territorial display or courtship
on Neanotis lancifolia
The flies of this family are commonly called Phantom Craneflies (not to be confused with Tipulidae). They come in various sizes, but the ones I am interested in from Mumbai are mostly small and thin, with white bands on legs. The adults rarely feed, while the larva feed on decaying organic matter in swampy areas.
|Pygmy Phantom Crane fly, image courtesy Vipin Baliga
This family is closely related to Micropezidae, which we talked about earlier. The flies in this family are called Cactus flies. They are very similar in appearance with Stilt-legged flies, but their forelegs are not reduced like that in Micropezidae. Their larvae feed on decaying vegetable matter, and adults are commonly seen near rotting fruits – this is in fact the best location to observe these flies.
|Cactus fly (red arrow), image courtesy Hari Iyer
These flies are commonly called Tachinid flies, and are somewhat hard to distinguish from many Muscoid flies. The larvae are parasitic, developing inside caterpillars of butterflies, or grubs of beetles, or nymphs of bugs and grasshoppers. The adults can be easily distinguished by the presence of many bristles all over the body.
|A typical Tachinid fly showing extensive bristle-like hair. This image
is for reference purpose only
This is another fly which is probably present in Mumbai. Commonly called Black Scavenger flies, they are more commonly seen feeding on dung. This is probably one reason why I have failed to observe them! These flies have a habit of waving their wings forward and backwards, much like the flies we will discuss below.
Most flies in this family have pictured wings, hence they are called Picture-winged flies, but many other flies (such as Bombyliidae and Tephritidae) are also mistakenly called Picture-winged flies. These flies are commonly seen sitting on branches, waving their wings, either as a territorial display or to attract females.
|A Picture-winged fly
|A common Picture-winged fly seen throughout Mumbai and
the surrounding areas
The flies in this family are called March flies, or Love bugs (although they are not bugs). The adults are pollinators, thus very important to the ecosystems, while the larvae can be pests on some vegetables and crops. Although I have not come across any records from Mumbai, I stumbled upon this picture taken by Satish Nikam at Mulshi (Pune). This is a good record not far from Mumbai; hence I have decided to include this family in the uncertain families section.
Another fly similar to the fly families discussed above bear resemblance to Muscidae and Tephritidae as well. The adults are common on decomposing vegetable and animals. It also requires further observations.
Also called Shore flies or Brine flies, these are commonly seen along beaches and near ponds. Although telling some species apart from other families in Musciodea is difficult, one unique genus Ochthera, inhabits Mumbai.
|Ochthera sp, commonly called Mantis fly, image courtesy Vipin Baliga
GNAT AND MIDGE FAMILIES
There are several families of these flies found all over the world. They are mostly small, mosquito-like flies that are either benign or parasitic. We have already seen benign non-biting midges, and the parasitic sandflies. Then there are Gall Midges and Gall Gnats (family Cecidomyiidae) that lay eggs in stems, leaves or flower buds, and develop inside – forming a gall like structure. The Gall Midges thus can be pests on some crops. There are Fungus gnats that fall in several families, Wood Gnats and Dixid midges amongst others. This group of families mostly goes unnoticed because of their small size.
There are other fly families such as Anthomyiidae that look very similar to Houseflies. These striking similarities as well as variations make Diptera a much complex and curious Order in Class Insecta. Only through keen interests of amateur naturalists and with the help of Dipterologists can we map this great diversity of such overlooked Order.
After looking at this great diversity, I am left with many questions in my mind, some sane, some metaphorical. I will keep questions like “will we discover a new species in Mumbai?” aside, and ask more general questions, such as “why aren’t flies studied as extensively as butterflies?” I already answered it in the introduction, but come to think about it, these flies do seem more interesting in their shapes, sizes, colours and behaviour than butterflies! We’re missing studying this great diversity shrouded in the magnificent wingspans of butterflies! (PS: No insect politics here). Jokes aside, it really is interesting to watch a Robberfly capture a Hoverfly since both are extremely aerodynamic, it is also interesting to observe Beeflies as they engage in territorial disputes.
|A Blowfly caught by a Jumping Spider
|A Bee fly caught by a Jumping Spider
|A Robber fly wit ha Syrphid fly kill
Now turning to some metaphoric questions, such as – why do only flies have to mimic other insects? I cannot recollect any insect that intentionally tries to mimic flies! Why do flowers with a butterfly sitting on it looks prettier than a fly sitting on a flower? We all know the answers, but today, lets raise a cup for the flies (the good and the bad), but make sure that none bite!
And a bonus picture!
|A Pygmy Dartlet feeds on a Tiger Mosquito as a Crematogaster Ant watches in awe!