Robber Fly/ Assassin Fly
Asilidae - Stenopogoninae
Kawal Tiger Reserve, Telangana
As part of my ongoing collaboration with the Hyderabad Tiger Conservation Society, I have been exploring the Kawal Tiger Reserve including the Gond villages within the area. I did some nightscapes in the vicinity of one of those villages published earlier but today is about one of nature’s best pest controllers and an almost unknown predator of these jungles - the Robbery Fly/ Assassin Fly from the genus Stenopogon. For identification, I had help from Asilidae research scholars & published authors Kavya G. Pillai (Christ College, Irinjalakuda) and Chris M. Cohen (North Carolina State University), who were able to narrow it down to the genus.
Telangana is the eleventh largest state in India situated on the south-central stretch of the Indian peninsula on the high Deccan Plateau. It is the twelfth-most populated state in India with a geographical area of 112,077 km² of which 21,214 km² is forest cover. The dry deciduous forests ecoregion of the central Deccan Plateau covers much of the state, including Hyderabad. The characteristic vegetation is woodlands of Hardwickia binata (Anjan Tree or నరేపా) and Albizia amara (నార్లింగ నల్ల రెంగా). Over 80% of the original forest cover has been cleared for agriculture, timber harvesting, or cattle grazing, but large blocks of forest can be found in the reserve areas like Kawal, Amrabad and the huge Nagarjuna Sagar - Srisailam Tiger Reserve. The more humid Eastern Highlands moist deciduous forests cover the Eastern Ghats in the eastern part of the state. The Central Deccan forests have an upper canopy at 15–25 meters, and an understory at 10–15 meters, with little undergrowth.
The Kawal Tiger Reserve located in the North Eastern part of Telangana (the old Adilabad district) is bounded by the mighty Godavari River on one side and the Maharashtra border on the other. It lies within the Jannaram mandal of Adilabad district. The Government of India declared Kawal Wildlife Sanctuary a Tiger Reserve in 2012 and HyTiCoS was a key influencer in this decision. At present the reserve has a low tiger density but promises tremendous potential as a source area with stepped up protection and habitat amelioration under Project Tiger. The Kawal Wildlife Sanctuary was established in 1965 and later declared as a Protected Area (PA) in 1999 under the WPA, 1972. Incidentally, when I went through my photographs over the years, I realized that a lot of the wild and birdlife I had photographed were from the areas in the Godavari River basin and its tributaries. Read about them here.
Kawal Tiger Reserve & the proposed Kumram Bheem Conservation Reserve
Kawal is well known for its abundant flora and fauna. The reserve is catchment for the rivers Godavari and Kadam, which flow towards the south of the sanctuary. The Kawal Tiger Reserve (KTR) is spread over a total area of 2015.44 km² of which the Core Area is 893 km² extending in the districts of Nirmal, Mancherial, Adilabad and Kumuram Bheem Asifabad. Geographically the reserve is situated in the southern-most tip of the Central Indian Tiger Landscape, having linkages with the Tadoba-Andhari (Maharashtra) and Indravati (Chhattisgarh) Tiger Reserve. Thus, the habitat has tremendous significance for tiger conservation in the region. After being listed as a Tiger Reserve in April 2012, it was developed as a tiger habitat with the release of 150 Chital as the prey population and today it is home to a whole multitude of species.
To reduce poaching, new check-posts have been created and traditional sources of water improved. HyTiCoS is also leading from the front conducting regular threat assessments and snare removal surveys, monitoring the Tigers which are in and passing through, conducting large-scale occupancy surveys and monitoring the prey base. They map corridors, conduct Bird Walks and Biodiversity Documentation Checklists and much more.
There has been an impactful decision taken on 30 May, 2025 - “The Telangana State government on Friday (May 30, 2025) issued orders declaring the tiger corridor area connecting the Kawal Tiger Reserve in the State with the Tadoba-Andhari Tiger Reserve in Maharashtra as the ‘Kumram Bheem Conservation Reserve’, as per the provisions of the Wildlife Protection Act, 1972… Apart from tigers, the proposed area is home to a variety of other carnivores such as leopard, wild dog, sloth bear, wolf, hyena, honey badger and jungle cat, and supports diverse prey such as gaur, sambar, nilgai, chital, four-horned antelope, muntjac, and Indian gazelle.”
Kawal Tiger Reserve
Biogeographically Kawal falls under the Deccan Plateau Zone (Zone VI). The forest vegetation of the core has been classified as “Southern Tropical Dry Deciduous Forest: Dry Teak Series and Southern Dry Mixed Deciduous Forests Series” (Champion and Seth, 1968). Teak is found extensively along with Bamboo. As many as 673 plant species have been recorded, and the important ones are Anogeissus latifolia commonly known as the Dhawa, Mitragyna parviflora commonly known as the Nerkadamb, Terminalia crenulata commonly known as the Crocodile Bark tree, Terminalia arjuna or the Arjun Tree, Boswellia serrata or Dhup tree, Sterculia urens commonly known as the Bhutyā (Ghost) tree, Terminalia belerica commonly called the Baheda, Madhuca indica or Mahua a favourite of bears, Cleistanthus collinus or Garra/ Toxic Gooseberry, Lannia coromondilica known as Moya/ Indian Ash Tree, Butea monosperma the stunning Palash/ Flame of the Forest, Calycopteris floribunda known as Kokkarai in Hindi and Bandi murugudu (బండి మురుగుడు) in Telugu, Zizyphus oenophile the Indian Plum or Makai, Acacia intisia known as Incha, Palinja or Soap Bark and the Diospyros melanoxylon or the Beedi leaf tree (తునికి) shown here on the right.
Beedi leaf tree (తునికి)
The important grass species include: Heteropogon contortus known as Oopu gaddi or Eragaddi (ఎర్రగడ్డి), the weed Apluda mutica known as Lapdu (లాప్డు) in Telugu, Saccharum spontaneum known as Rellugaddi (రెల్లుగడ్డి) or Kaki Cheruku (కాకి చెరకు), Oplismenus composites called Kodijuttugaddi (కోడిజుట్టుగడ్డి), Dicanthium annulatum known colloquially as Angadi Gaddi (అంగడి గడ్డి), which translates to "ringed grass" or "marvel grass". Another common name in Telugu is chinnagaddi (చిన్న గడ్డి) and Themeda species known as Chikati Gaddi (చీకటి గడ్డి) or "Aavu Gaddi" (ఆవు గడ్డి). The reserve has considerable weed growth of Cassia tora, Hytis suovalens, Cleome viscosa and Lantana camara.
Kawal has faunal diversity typical of the Deccan Plateau. Zoo-geographically, the reserve comes under the Indo-Malayan region, and the major wild animals include: Nilgai, Chausingha, Chinkara, Black Buck, Sambhar, Chital, Wild Dog, Wolves, Jackals, Foxes, Jungle Cats, Leopards & the umbrella species - Tiger. Besides these big ticket species there are 23 orders of insects, 10 species of amphibians belonging to three families, viz. Bufonidae, Ranidae and Rhacophoridae; 34 species of reptiles out of which 14 belong to order Testudines, 13 to order Sauria and 7 to order Serpentes. As many as 260 species of avifauna belonging to 18 Genera, 51 families and 75 species of Mammals belonging to the orders of Insectivore (2), Chiroptera (25), Primates (4), Carnivora (17), Artiodactyla (10), Rodentia (15), Lagomorpha (2) are found. The bird life too is abundant with numerous Peacocks, Bulbuls, Partridges, Quails, Flycatchers, Thrushes, Hawk-Cuckoos, Eagles, Vultures to name a few of the 242 bird species reported here.
Tiger Status
Compared to the older Tiger Reserves like Corbett or even Nagarjuna Sagar - Srisailam, Kawal is a more recent notification as a tiger reserve, with tremendous scope for consolidating the core area vis-à-vis the guidelines of Project Tiger. The important managerial thrust areas include stepped up protection through reinforced protection infrastructure in the form of patrolling camps, wireless network, foot patrolling and vehicular patrols. Further, the core area needs to be made inviolate through voluntary relocation of human settlements to foster a viable population of tiger. The buffer has a multiple use agenda to address co-occurrence of wild animals and people. The livelihood options to people are important through ecologically sustainable viable options through sectoral integration. The wildlife concerns need to be mainstreamed in forestry operations.
The Kawal Tiger Reserve has connectivity to the Tadoba-Andhari Tiger Reserve of Maharashtra in the North, to the Indravati tiger reserve of Chhattisgarh towards its North-Eastern side and the Tipeshwar Wildlife Sanctuary to the North-West. Portions of the Bellampalli territorial division (Kukkudhatti-Ada area) borders Maharashtra. Likewise, the forests of Bijjur and Kagaznagar have connectivity towards the Chapparala Wildlife Sanctuary of Maharashtra leading to Indravati Tiger Reserve (Chhattisgarh).
Read about some of the magnificent Tigers from Central and South India.
Threats
Sand mining, poaching, destruction of teak forests, migratory cattle, vehicular disturbance, lack of water and fodder were and still are major threats in the reserve. The lack of sand in nearby villages and towns led to the main problem of sand mining within the forest range. But with help from political leaders, the unrelenting endeavors of the staff from the Forest Department and HyTiCoS and the continued support of the villagers the situation has been controlled to some extent, however it is a constant threat. The presence of teak and bamboo too is a primary threat leading to habitat destruction due to felling and smuggling. These threats have been controlled by the establishment of base camps in the interior forest areas and deploying strike forces and anti-poaching squads. All vehicular traffic is restricted between 2100 hrs and 0600 hrs on the roads passing through the tiger reserve and heavy vehicular traffic of certain categories is prohibited at all times on these roads.
Fire is another managerial issue as the entire area is fire prone and burns almost twice in the hot season. Attempts have been made to enhance the habitat by improving the status of water availability in the reserve through increasing the number of percolation tanks, check dams, by repairing old structures, and repairing the major breached tanks, maintenance of saucers and natural water holes. Though the rain fall varies between 900 mm to 1100 mm, almost the entire water from the rains drains into the River Godavari within hours due to the slope of the land. 55%-60% of area is occupied by Cassia tora (Chakunda), Hyptis suovalens (Chia) and Lantana camara (Lantana). Attempts have made to reduce the dominance to expose the ground and to improve the status of grasses/ fodder in the reserve. There are 10-12 villages inside the core area and attempts are being made to relocate them to areas adjoining the forest - a herculean task by any measure. Once the villages are relocated the issues of meadows and the fodder problem may be solved in addition to making the area inviolate.
Robber Fly - Asilidae - Stenopogoninae
Robber Flies (Diptera: Asilidae) comprise one of the largest groups of extant flies (Hull, 1962). Asilids constitute more than 500 genera (Woodley, 1989) and more than 5500 species (Lehr, 1988) with a worldwide distribution except Antarctica. Species range in size from less than 1 cm to nearly 8 cm in length, and their prey consist of both small and large insects caught largely in flight. Asilid color patterns are simple: usually black, gray, or bronze, although some more colorful species appear to mimic bees and wasps.
India is the largest country in South Asia and the seventh largest globally in terms of area (>3.2 million km²; GOI 2024). The diverse affiliations the Indian landmass has had throughout its geological history are reflected in the Indian biota, a unique mix of Gondwanan, Southeast Asian, African, and Palearctic elements (Sidharthan & Karanth 2021). With four biodiversity hotspots — the Himalaya, the Western Ghats, Indo-Burma, and Sundaland — and a home to 7–8% of all known species, India is one of the world’s megadiverse countries (Myers et al. 2000; CBD 2024). Rodgers & Panwar (1988) classified India into ten distinct biogeographic regions. Up to now, these biogeographic areas have yielded records for 103,920 animal species and 55,387 plant species (Banerjee et al. 2023; Mao et al. 2023).
Insects make up over two-fifths (42%) of India’s known biodiversity, with 66,747 currently documented species (Banerjee et al. 2023). The entire extent of the Indian entomofauna, however, is unknown because many insect groups are still poorly understood and most Indian regions have not been thoroughly investigated and recorded for insect taxa. As a result, the species richness in the country is expected to be much greater than what is currently known (Shah et al. 2014; Wachkoo et al. 2017; Yatoo et al. 2021). As new studies and investigations expand our understanding of India’s insect biodiversity, comprehensive taxonomic revisions and inventories are still lacking (Ballal et al. 2018; Akbar et al. 2022; Yatoo et al. 2022). One such group is the insect family Asilidae, on which there is substantially incomplete and fragmented knowledge in the country.
Currently, there are about 7,500 described species of Asilidae (robber or assassin flies) distributed all over the world (Pape et al. 2011) in the order Diptera, the true flies. Asilidae are cosmopolitan and important in maintaining community equilibrium because they prey on and manage populations of arthropods and insects. They are currently being regarded as a practical substitute for pest control in Integrated Pest Management (Joern & Rudd 1982; Wei et al. 1995).
The common name Robber Flies was first suggested in 1869 by Alpheus Packard based on the German “Raubfliegen” (predatory flies). Latreille was the authority for establishing the family in 1802. The Asilidae, together with Bombyliidae and Therevidae, are the most representative families of the superfamily of Asiloidea and they form one of the most characteristic groups of the lower Brachycera.
Robber flies have stout, spiny legs and three simple eyes (ocelli) in a characteristic depression on the tops of their head between their two large compound eyes. They also have a dense moustache of stiff bristles on the face; this is called the mystax, a term derived from the Greek mystakos meaning "moustache" or "upper lip". The mystax has been suggested to afford some protection for the head and face when the flies deal with struggling prey. Various Asilidae prey on formidable species including stinging Hymenoptera, powerful grasshoppers, dragonflies and even other Asilidae – practically anything of a suitable size. Some Asilidae do, however, specialize in smaller prey, and this is reflected in their more gracile build.
In general, the family attacks a very wide range of prey, including other flies, beetles, butterflies and moths, various bees, ants, dragonflies and damselflies, ichneumon wasps, grasshoppers, and some spiders. They seem to do so irrespective of any repugnatorial chemicals the prey may have at their disposal. When attacked, many Asilidae do not hesitate to defend themselves in turn using their probosces and may deliver intensely painful bites to humans if handled incautiously. The antennae are short, have three segments, and sometimes bear a bristle-like structure called an arista.
Though they are a very characteristic group for such a large family, the Asilidae may easily be confused with the related and less widely known family Therevidae. Some points of contrast between the families include that the labium in the Therevidae is not a piercing, predatory organ, but ends in two fleshy labella adapted to the sucking of liquid foods. Again, the Therevidae commonly have fluffy setae above the mouthparts, unlike the stiff chaetae comprising the mystax of the Asilidae. Furthermore, in the Asilidae the depression on the vertex between the eyes tends to be more obvious than in the Therevidae.
The fly attacks its prey by stabbing it with its short, strong proboscis, injecting the victim with saliva containing neurotoxic and proteolytic enzymes which very rapidly paralyze the victim and soon digest the insides; the fly then sucks the liquefied material through the proboscis. Many Asilidae have long, tapering abdomens, sometimes with a sword-like ovipositor. Others, for instance Laphria, are fat-bodied bumblebee mimics.
Female robber flies deposit whitish-colored eggs on low-lying plants and grasses, or in crevices within soil, bark, or wood. Egg-laying habits depend on the species and their specific habitat; most species lay their eggs in masses, which are then covered with a chalky protective coating. After hatching, robber fly larvae generally seem to live in soil, rotting wood, leaf mold, and similar materials, some being predatory and others detrivorous. Larvae are also predacious, feeding on eggs, larvae, or other soft-bodied insects. Robber flies overwinter as larvae and pupate in the soil. Pupae migrate to the soil surface and emerge as adults, often leaving behind their pupal casing. Complete development ranges from one to three years, depending on species and environmental conditions. Stenopogon is a genus of robber flies, insects in the family Asilidae. There are at least 200 described species in Stenopogon.
The most recent work covering the entire Indian fauna was published as part of a catalog to the Oriental region by Joseph & Parui (1983a). These authors later published the first volume of a more specific catalog of the Indian subcontinent (Joseph & Parui 1998), but never published the second volume. It has thus been over 40 years since the Indian species were treated in a single work, and a comprehensive catalog specifically of the Indian fauna has never been published. As new scholars begin studying the diverse robber fly fauna of India, the need for an up to date catalog of all species has become apparent. This paper attempts to address this shortcoming and serve as a foundation for future studies of Asilidae in India. This contribution goes beyond the scope of earlier works in that it presents:
a comprehensive inventory of the Indian Asilidae fauna, with updated taxonomy, as well as brief information on all known type localities, depositories, including synonyms;
extensive synoptic data on geographical occurrence records in India;
a list of excluded species, with notes; and
indications of putatively endemic taxa.
Yatoo et al., specifically Suhaib Firdous Yatoo, Aijaz Ahmad Wachkoo, Kavya G. Pillai, and Chris M. Cohen, are known for their work on the catalog of robber flies (Asilidae) of India. Their research, published in Zootaxa, provides a comprehensive listing of robber fly species found in India, including new records and insights into the distribution and taxonomy of these insects. A catalog of the species of Asilidae occurring in modern India is provided, based primarily on an extensive review of relevant literature. They have reported nine subfamilies, 60 valid genera and 478 valid species present in India; 368 species (77%) of the fauna, are currently only known from India and may be endemic, while 27 more species have been removed from the Indian list. The catalog entries provide taxonomic, synonymical, nomenclatural, and geographic information for all species taxa. This work represents just the first step in what must be a thorough and systematic review of the Indian Asilidae fauna. Their published paper is linked below.
Adults are generally medium to large in size, with an average body width of 1 to 1.5 cm (0.39 to 0.59 in), but with a range of 3 mm (0.12 in) to more than 5 cm (2.0 in) in length. The shape is generally elongated, due to the conformation of the long tapering abdomen, however there are also compact species with broad abdomens. The integument is covered with thick hair, especially on the head and thorax and liveries are often showy, with colors ranging from brown to black to grey, sometimes in contrast with other colors such as red and yellow. Frequently they are aposematic, imitating the livery of Hymenoptera.
The head is free and mobile and dichoptic in both sexes and has three ocelli arranged in a characteristic depression formed by the elevation of the compound eyes. This feature is clearly visible in the front view and is a morphological peculiarity of Asilidae. The occipital region has one or more rows of bristles aligned behind the posterior margin of the eye. The facial region has a convex profile with a characteristic dense bundle of bristles, called a mystax. The mystax helps protect the head and face when the fly encounters prey bent on defense. Other bristles are arranged on the ocellar tubercle.
The antennae are of the aristate type, composed typically of five segments but sometimes from three to four, depending on the structure of the stylus. The scape and pedicel are generally relatively short and hairy; the third segment (or first flagellomere) has an oval or oblong shape, is generally longer than the two basal segments, and bears a stylus generally composed of two segments, of which the basal is very short. In some asilids, the stylus can be monoarticolate or absent.
The mouthparts are short, being modified for piercing and sucking. The strongly sclerotized proboscis is composed of the labium and maxillae which form a food canal, the labrum and a piercing organ, the hypopharynx. The proboscis is either rounded in cross section or compressed laterally or dorsoventrally; it is usually stout and straight and is sometimes able to penetrate through the hard integument of Coleoptera. The maxillary palpi are at the base beside the labium, two-segmented in all Dasypogoninae or single segmented in Asilinae and Leptogastrinae.
The thorax is robust and compact. Unlike in other lower Brachycera, it bears long bristles (macrochaeta) useful as taxonomic characters. Bristles of this type are always present on the notopleuron (notopleural bristles) and, in two series, on mesonotum (dorsocentral, supralar and postalar). Other bristles are present on the metanotum (dorsocentral), bristles on the ventral episternum and at the apex of the mesoscutellum.
The legs are relatively long and strong, with many macrochaetes performing a raptorial function. The wings are well developed, often relatively narrow for speedy flight; the alula is generally well developed, with the exception of the Leptogastrinae and part of Dasypogoninae. The venation is much as in the Rhagionidae, Tabanidae, and Therevidae; the radial R is always four-branched, with R2+3 unbranched. Details of wing venation determine subfamilies and lower taxa. The wings are most often hyaline, but sometimes smoky or dark colored, or partly infuscated in many genera or completely darkened. The abdomen consists of six to eight visible segments preceding the genitalia in males, but the eighth segment is sometimes entirely or partially concealed, and terminal forming the ovipositor. It is long and narrow conical in most species, but wide, dorsoventrally flattened and short in bee mimics. In the Leptogastrinae, the abdomen is extremely long and slender. In some tribes, the male undergoes axial torsion of 180°. The egg is hyaline or pigmented, of variable shape from spherical to oval, and up to 2 mm in length. The surface can be smooth or bear microsculptures, which are generally polygonal and visible only in the electron microscope. The larva is apodous, cylindrical, and elongated, more or less flattened dorsoventrally and tapered at the cephalic and caudal ends. The colour is white or yellowish. The head is small, rugged, dark-pigmented and hypognathous, while the abdomen is composed of eight apparent urites, with the last two often fused and more or less reduced. The respiratory system is amphineustic, with two pairs of spiracles, one thoracic and one abdominal. Also, rudimentary and nonfunctional stigmata occur in other abdominal segments. The pupa is naked, as in the majority of the Orthorrhapha, exarate and therefore able to move.
The Asilidae are predators, in both the juvenile and the adult stages, and feed on small arthropods, mainly insects. Although predatory forms in the adult stage are present in other taxonomic groups of Diptera, the Asilidae are the most representative for the number of species and for uniformity of feeding behavior (>7000 species, all of which are predatory). The combination of high biodiversity and high predatory activity leads to this family playing an important role in the ecological stability of entomofauna. The life cycle takes place in 1–3 years. The postembryonic development consists of four larval stages (instars) and one pupa. The larvae of the first instar differ from other stages in both ethology and trophic regime. The larvae of most known asilids live in the soil or in the case of some taxonomic groups, in rotting organic material, usually wood and the bark of dead trees.
With regard to feeding behavior, most of the literature describes Asilidae larvae as entomophagous, but doubts remain about the real nature of the trophic regime and its mechanisms. The entomophagy of some species had indeed been already hypothesized by some authors of the 19th century, based on the findings of larvae of asilids associated with larvae of other insects, but Melin (1923) asserted that, in reality, predation was occasional and secondary to the plant-based diet. More recent studies have confirmed the entomophagy of some asilids without extending this species' feeding behavior for the whole family. Less certain, however, is the mechanism of entomophagy: in general, the behavior is cited as predation, but for some species may be ectoparasitoids. Musso (1983) described the feeding behavior of the larvae of Machimus rusticus: the larvae of the first instar does not feed on insects, those of the second instar feed on secretions by larvae of beetles (and may cause death), while the larvae of the third and fourth instars actually behave like predators. In short, the feeding behavior of larval asilids can be intermediate between predation and ectoparasitism.
Much better known and described in detail is the behavior of adults. In general, predation in adults is concentrated in the hottest hours in open, sunny spaces, while at night, they take refuge in dense vegetation. The Asilidae are excellent flyers, and in most of the family, capture prey in flight. They are often seen stationed to ambush prey at strategic points. This behavior signifies that sight plays an essential role in the detection of prey and their capture.
The prey is caught with the tarsi and injected with a paralyzing saliva. The asilid pierces the integument of the prey with the prepharynx (hypopharynx) in preferential points of least resistance such as the eyes, the membranous area of transition between the head and thorax (neck) or between thorax and abdomen, or between the last abdominal tergites. Puncture is followed by the injection of saliva, whose active components perform two functions: neurotoxins cause paralysis of the victim, while proteolytic enzymes lead to the breakup and liquefaction of internal tissues. In a short time, the predator is able to feed by sucking the internal fluids through the alimentary canal.
With regard to interspecific trophic relationships, a large number of reports exists on the prey captured by the Asilidae. Lavigne (2003) has developed a database comprising over 13,000 reports. The prey of Asilidae are predominantly represented by other insects, mostly winged, but several cases in which they have attacked spiders have also been reported. Within the insects, orders that include the most frequent prey of asilids include a wide range of families within the Coleoptera, Hymenoptera, other Diptera, Hemiptera, and Lepidoptera; prey belonging to various other orders (Odonata, Neuroptera, Isoptera, Thysanoptera, Blattodea, etc.) are also mentioned.
With regard to the specificity of the trophic relationship, Wood (1981) mentions some studies in the literature on the subject. Some genera have been found to be monophagic, but more generally Asilidae are polyphagic, with behaviors that vary from narrow specialization to broad prey choice. Other studies have shown that the ratio between the size of the prey and the asilid varies from 1.8:1 to 3.7:1, with an average of 2.6:1. The ratio tends to increase with decreasing size of the predator.
Egg-laying takes place, according to the species, with three different behaviors that relate to the structure and the morphology of the abdomen. Females with an undifferentiated ovipositor release eggs randomly and independently from the substrate. In other cases, however, the abdomen bears a differentiated, specialized ovipositor to lay eggs in the soil or sand, or lay them in cavities within plant tissues.
Asilidae generally occur in habitats that are open, sunny, and dry, even arid. They favour open or scattered vegetation, and some species even frequent bare ground. Typical habitats include savannah, forest steppe, open steppe, semidesert, maquis shrubland, and related shrubland types such as fynbos and chaparral. Their biodiversity is lower in forested ecosystems, and where asilids do occur in such environments, they tend to concentrate in the glades and margins. In those conditions, the interrupted canopy leaves space for various species of shrubs and herbaceous plants suited to asilid styles of predation.
In general, the biology of the Asilidae is still poorly known, but various authors have studied the population distribution in particular regions and ecosystems. They have classified the behavioral patterns in terms of micro environments, ecological, and trophic factors, showing how different species of Asilidae favour particular habitats suited to particular patterns of reproduction and predation. Specific studies show correlations between the floristic composition and predatory behaviour.
Asilidae occur in all zoogeographical regions except Antarctica. In the Northern Hemisphere, some species are even adapted to tundra. Alpine species occur at altitudes exceeding 4000 meters/13,000 feet. However, the highest levels of biodiversity are in warm climates; tropical or subtropical and arid or semi-arid regions tend to have the greatest variety of species, followed by areas where rainfall is highly seasonal.
The Asilidae currently include over 7500 described species in about 556 genera. Their taxonomy is still under study in the light of new specimens and cladistic analysis. The 14 accepted subfamilies are:
Asilinae
Bathypogoninae
Brachyrhopalinae
Dasypogoninae
Dioctriinae
Laphriinae
Leptogastrinae
Ommatiinae
Phellinae
Stenopogoninae
Stichopogoninae
Tillobromatinae
Trigonomiminae
Willistonininae
The oldest known member of the family is Araripogon from the Early Cretaceous (Aptian) Crato Formation of Brazil. Stenopogoninae is another subfamily of robber flies in this family. There are 76 genera and 740 described species in Stenopogoninae. The 76 genera are:
Afroscleropogon Londt, 1999
Anarolius Loew, 1844
Anasillomos Londt, 1983
Ancylorhynchus Berthold in Latreille, 1827
Anisopogon Roeder, 1881
Araujoa Artigas and Papavero, 1991
Archilestroides Artigas and Papavero, 1991
Argyrochira Richter, 1968
Astylopogon Meijere, 1913
Aymarasilus Artigas, 1974
Backomyia Wilcox and Martin, 1957
Bana Londt, 1992
Callinicus Loew, 1872
Connomyia Londt, 1992
Corymyia Londt, 1994
Creolestes Hull, 1962
Crobilocerus Loew, 1847
Cylicomera Lynch Arribálzaga, 1881
Cystoprosopa Hull, 1962
Danomyia Londt, 1993
Dapsilochaetus Hull, 1962
Daspletis Loew, 1859
Dasypecus Philippi, 1865
Dicranus Loew, 1851
Dioctobroma Hull, 1962
Dogonia Oldroyd, 1970
Empodiodes Oldroyd, 1972
Enigmomorphus Hermann, 1912
Eriopogon Loew, 1847
Eucyrtopogon Curran, 1923
Euthrixius Artigas, 1971
Fishermyia Londt, 2012
Galactopogon Engel, 1929
Gonioscelis Schiner, 1866
Grajahua Artigas and Papavero, 1991
Graptostylus Hull, 1962
Grypoctonus Speiser, 1928
Hadrokolos Martin, 1959
Haroldia Londt, 1999
Harpagobroma Hull, 1962
Hystrichopogon Hermann, 1906
Illudium Richter, 1962
Iranopogon Timon-David, 1955
Itolia Wilcox, 1936
Ivettea Artigas and Papavero, 1991
Jothopogon Becker in Becker and Stein, 1913
Leptochelina Artigas, 1970
Lithoeciscus Bezzi, 1927
Lonquimayus Artigas and Papavero, 1991
Microstylum Macquart, 1838
Neodioctria Ricardo, 1918
Neoholopogon Joseph and Parui, 1989
Neoscleropogon Malloch, 1928
Nothopogon Artigas and Papavero, 1991
Oldroydella Özdikmen, 2006
Ontomyia Dikow and Londt, 2000
Oratostylum Ricardo, 1925
Ospriocerus Loew, 1866
Plesiomma Macquart, 1838
Pritchardia Stuardo Ortiz, 1946
Pritchardomyia Wilcox, 1965
Prolepsis Walker, 1851
Pycnomerinx Hull, 1962
Raulcortesia Artigas and Papavero, 1991
Remotomyia Londt, 1983
Rhacholaemus Hermann, 1907
Rhayatus Özdikmen, 2006
Scleropogon Loew, 1866
Scylaticina Artigas and Papavero, 1991
Scylaticodes Artigas and Papavero, 1991
Scylaticus Loew, 1858
Sintoria Hull, 1962
Stenopogon Loew, 1847
Taperigna Artigas and Papavero, 1991
Wilcoxia James, 1941
Zabrotica Hull, 1958
Despite the considerable popularity of robber flies, and a rich history of extensive research on asilid morphology, taxonomy, and behavior (Bigot, 1857; Bromley, 1932; Enderlein, 1914; Hull, 1962; Karl, 1959; Loew, 1847; Leach, 1819; Macquart, 1838; Martin, 1968; Oldroyd, 1969; Osten Sacken and Baron von, 1884), a comprehensive phylogenetic hypothesis for the subfamilies has yet to emerge. Recent attempts to produce a phylogenetic hypothesis at this level have been based on intuition rather than a quantitative phylogenetic analysis (Lavigne et al., 1978; Papavero, 1973; Wood, 1981; Woodley, 1989) and have not received universal acceptance. Various authors have identified characters that may be useful in a phylogenetic analysis. These include features associated with palpal segments and female genitalia (Williston, 1908), marginal cells of the wings (Bromley, 1932; Engel, 1928), presence or absence of an apical spur on the foretibia (Loew, 1847; Hull, 1962), hair on the katatergite, and antennal segmentation and structure (Papavero, 1973). However, since none of these characters have ever been formally coded nor tested cladistically, their utility in deciphering asilid phylogeny has yet to be demonstrated. Moreover, the characters used to define subfamilies have never been assessed across the entire diversity of robber flies, and many groups do not fit well within these subfamilial groupings (Carrera, 1949; Hardy, 1948; Hermann, 1926; Williston, 1908).
Papavero (1973) presented an intuitive phylogeny for asilid subfamilies, in which he organized the subfamilies into four major groups. The leptogastrinae-group, occupied solely by the subfamily Leptogastrinae, is characterized as having a long slender abdomen with the alula and pulvilli lacking. The asilinae-group consisting of the three Asilus-like subfamilies Asilinae, Ommatiinae, and Apocleinae, are characterized as having closed marginal wing cells and slender antennae. The laphriinae-group is comprised of the Laphria-like subfamilies Laphriinae and Laphystiinae, and is characterized as having closed marginal wing cells and clubbed antennae. The remainder of Asilidae is composed of morphologically diverse taxa placed in the dasypogoninae-group, including the subfamilies Dasypogoninae, Trigonomiminae, Stichopogoninae, and Stenopogoninae. This group is characterized by the presence of open marginal wing cells and an apical spur on the fore tibia. The characters supporting Papavero’s hypothesis are controversial, and there is a diversity of opinions among dipterists over the validity of these groups (Hardy, 1948; Hull, 1962; Martin, 1968; Oldroyd, 1969; Wood, 1981).
From an identification standpoint, in the images I took, the wings were not too clear making it difficult to identify beyond the genus. Venation is not clear and it is a critical component to know whether the veins are fused or not. Beyond that their huge body and mystax help to narrow it down to Stenopogon. Female terminalia in Stenopogoninae usually have tiny spine like structures.
In India: Robber flies of the genus Stenopogon have been recorded from various locations in West Bengal, including Jalpaiguri, Kalimpong, Kurseong, and Alipurduar, as well as Tamil Nadu, Kerala, Orissa, Telangana, Andhra Pradesh and Rajasthan.
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