DIVERSITY OF FLOWER· VISITING FLIES (INSECTA: DIPTERA) IN INDIA AND THEIR ROLE IN POLLINATION

Nectar is one of the most important foods for majority of dipterans with respect to adult energetic requirements for flight in dispersing, finding mates, mating, and searching sites for oviposition (Larson et aI, 2001). The flies therefore spend much of their time on flowers. The true flies of late Jurassic period with long mouth parts also support their nectar feeding ability. Many species of Diptera visit flowers, and their abundance on plants could indicate their importance as pollinators as well as the importance of flowers in their diet. So knowledge on dipteran flower visitors is required as they perform vital role in pollination.


INTRODUCTION
Nectar is one of the most important foods for majority of dipterans with respect to adult energetic requirements for flight in dispersing, finding mates, mating, and searching sites for oviposition (Larson et aI, 2001).The flies therefore spend much of their time on flowers.The true flies of late Jurassic period with long mouth parts also support their nectar feeding ability.Many species of Diptera visit flowers, and their abundance on plants could indicate their importance as pollinators as well as the importance of flowers in their diet.So knowledge on dipteran flower visitors is required as they perform vital role in pollination.

DIVERSITY OF FLOWER• VISITING FLIES
Flies are one of the major successors of the insect world, and classified into about 10,000 genera, 150 families, 22-32 superfamilies, 8-10 infraorders and 2 suborders: Nematocera and Brachycera (Yeates & Wiegmann, 1999).A preliminary estimate (Buchmann & Nabhan, 1998) indicates that 14,126 species of Diptera are involved in the process of pollination in the tropical world.Inouye (2001) stated that the diversity of Diptera can rival or exceed of Hymenoptera in tropical areas.A total of 42 families (Nematocera 12 and Brachycera 30) of Diptera are reported as pollinators in the tropical world (Roubik, 1995), of which 37 families (Nematocera 12 and Brachycera 25) are found in India.
Flies that are confirmed as polliantors differ widely in their effectiveness.About one third of Nematoceran families obtain food from flowers, as well as other sources (Gilbert & Jervis, 1998;Larson et al. 2001).

Obligate nectar-feeders occur apparently in tropical
Culicidae (Snodgrass, 1959;Schremmar, 1961) and Simuliidae (Gilbert & Jervis, 1998).These primitive flies mainly visit flowers with readily accessible nectar in tubes that are short or somewhat hidden.The Brachycera contains wider variety of flower visitors and nectar-feeders which are mostly widespread in lower Brachycera.Obligate nectarivorous flies are recorded in Bombyliidae (Gilbert & Jervis, 1998).Moreover, there are some species of long-tongued families that visit deeper tubed flowers.It has also been observed that most of the cyclorrhaphan families are nectarivorous.
The following dipteran families are reported as flower visitors and pollinators in India Family BOMBYLllDAE Bee flies have generally been considered to be primarily nectarivorous although it has been known for some time that at least some bombyliids consume pollen.They are one of the important pollinator families of Diptera, which have long, sucking mouthparts especially suitable for visiting tubular flowers.Some of the recent works on bee flies in India are contributed by Mitra & Parui (2002), Mitra et al. (2005,  2006) and Banerjee & Mitra (2002).Their studies revealed that the bee flies are mostly attracted to the plants of Solanaceae family (Table-I).Little is known about diurnal activities of bee flies.Mitra et al. (2006)  stated that the bee flies are active throughout the day which supports their effective role in pollination.
Banerjee & Mitra (2002)  Their pollination ability is not well studied thoroughly.
12 species of calliphorid flies are reported as flower visitors and pollinators in India.Priti (1998), Priti & Sihag   (1997, 1998) observed that blowflies are the major pollinators of onion, carrot and cauliflower after bees Sharma & Thakur (1997) also recorded Lucilia sp. as a pollinator of a medicinal herb (Ammi majus Linn.).Bhatnagar (1986) recorded 4 species of blow flies as pollinator of Asclepiadaceae from Central India.

Family CERATOPOGONIDAE
The Ceratopogonidae, commonly known as biting midges, no-see-ums or punkies have a bad reputation as being nasty biters that pester humans and domestic animals and in some instances, transmit harmful diseases.However, few people realise that this group of flies provide some important services in ecological systems.Some species are important pollinators of plants such as cacao and rubber trees.But little is known about their foraging activities in India.Bhatnagar (1986) reported only 2 species of the genus Forcipomya as pollinators of Asclepiadaceae from India.

Family CULICIDAE
Mosquitoes are small and delicate.The adult females are pests to humans and many other animals as they feed on blood.Adult mosquitoes occasionally obtain nectar from flowers, but they are not significant pollinators in temperate climate.Usually male mosquitoes frequent flowers more than females.Nothing is known on the pollination ability of mosquitoes in India.Recently Mitra et al (2005) recorded one species of Culex as flower visitor of Polygonum chinensis in West Bengal.
Family DIOPSIDAE Diopsids, commonly known as stalk-eyed flies, are generally distributed throughout the World.Adults are easily identified by their characteristic eye stalks, found in all taxa, although the stalk lengths vary considerably.Barring a single species of diopsid fly as flower visitors of family Asclepiadaceae (Bhatnagar, 1986) nothing is known about other species.
Family DROSOPHILIDAE These small, delicate-looking tan or brown flies occasionally suck nectar from flowers, but they are more likely to visit rotting fruit or fermenting sap.They are not referred as a significant pollinator group of Diptera.Bhatnagar (1986) reported only one species as pollinator of Cosmostigma racemosum (Family Asclepiadaceae) from Dehradun.(Table-I)

Family MUSCIDAE
The members of this family are stout, robustly-built, medium-sized, grey or black, with darker stripes and other patterns.The adults occasionally visit flowers with exposed nectaries, particularly in the Carrot family.Altogether 19 species of house flies reported as flower visitors and pollinators from India.Priti  (1998), Priti & Sihag (1997, 1998), Mishra & Kumar (1993) stated that the members of this family are the important pollinators of cauliflower, carrot, onion, rape seed, almond etc. Bhatnagar (1986) identified 10 species of house flies as pollinators of Asclepiadaceae.Mitra et al. (2002Mitra et al. ( , 2004) also collected muscid flies from the flowers of garden, orchard, and agricultural plants.Mitra et al. (2006) reported two species of muscids as a pollinators of medicinal plants.
Family OESTRIDAE Species of Gasterophilinae of the Family Oestridae are commonly known as horse bot flies.They are medium-sized to large, rather thickset flies, the body covered with dense short or long hair, without thick bristles.Oestrid flower visitors got 7th rank as per their efficiency in pollination of cauliflower and carrot.(Priti & Sihag, 1997, 1998).

Family SARCOPHAGIDAE
The Sarcophagidae, commonly called as "flesh flies" comprises a group of medium-sized to fairly large and generally grayish to black flies.The adults occasionally feed on flowers with exposed nectaries.Priti (1998), Priti & Sihag (1997, 1998) reported sarcophagid species as pollinators of onion, cauliflower, and carrot.In all the studies Sarcophaga sp was ranked 6 th as per pollinating efficiency.

Family SEPSIDAE
The Black Scavenger Flies are small, shiny black, with round heads and base of abdomen strongly constricted.The most common genus, Sepsis, has a pigmented spot on the tip of the wing.This family is not recognised pollinator group and only 4 species have been reported as pollinators of the family Asclepiadaceae from India (Bhatnagar,1986).
Family STRATIOMYIDAE Soldier flies are true flies which often superficially resemble wasps in their appearance and behaviour.
However, these flies do not bite or sting.Adults are pollen or nectar feeders.The members of the family are well known flower visitors and pollinators.But only 3 species of soldier flies are so far reported as flower visitors and pollinators from India.Mitra et al. (2006) observed that the foraging activity of Adoxomyia heminopla is mostly restricted in early morning and they are the common visitors of the flowers of upper canopy.They are also found to visit the flowers of Tagetes patula (Mitra et al. 2005).(1997,1998) also observed the pollinating efficiency of hover flies on cauliflower, carrot and onion.Several workers like, Kumar & Kumar (1997), Mishra et al. (2004), Sharma & Thakur (1997), Mitra et al. (2003Mitra et al. ( , 2004Mitra et al. ( , 2005) ) have also studied the syrphid pollination.Recently, Mitra (unpublished) collected 3 syrphid species as flower visitors of Foeniculum and Anthemum spp. of the family Umbelliferae from Uttar Pradesh.

Family TABANIDAE
The tabanids or horse flies are stout, bristle less, medium to large-sized flies (5-25 mm long) belonging to the suborder Brachycera.The eyes are large, covering most of the head.The adults may obtain nectar from flowers, but are not important pollinators.The adult Horseflies are more likely to use flowers as a place to perch.Only two species are reported from India as pollinators.Priti (1998)   It is hoped that more and more works will take up the studies on the important aspect of pollination and pollinators especially dipterans and this work can serve as ground work for future research work
reported 30 species of flies from the flowers of Zizyphus mauritiana.But most of the studies in India on fly pollination have been made with other insect pollinator groups and research activity on flower visiting flies remained in a state of neglect.Therefore, it is imperative to prepare an inventory of flower visiting flies involved in the process of pollination of different plant species.Keeping in view, the Diptera section of Zoological Survey of India has initiated a study to generate the basic data on the flower-visiting flies of India.This communication has culminated in documenting 116 dipteran species belonging to 16 families as flower visitors and pollinators of 92 plant species (Table-I).
have collected 7 species of bee flies as flower visitors of agricultural crops from Arunachal Pradesh.Altogether 18 species of flower visiting bee-flies are reported from India.Recently, Mitra (unpublished) collected one bombyliid species from the flowers of Foeniculum and Anthemum spp.(Family Umbelliferae) in Uttar Pradesh.Family CALLIPHORIDAE Flies of the family Calliphoridae are stout, medium to large sized, with shiny metallic coloration, and commonly known as green bottles or bluebottles and blowflies.Adult blowfly feeds on nectar, honey dew and other sweet liquid or liquid products of organic decomposition.They are mostly active during day time.
and wasps.According to Mitra & Parui (2002) blowflies are the common flower visitors of cultivated and noncultivated plants.Moreover, Mitra et al. (2005) identified 3 species of calliphorid flies as pollinators of medicinal plants in West Bengal.Mitra et al. (2006) observed a large number of Stomorhina discolor hovering on the flowers of Zizyphus and Anogeissus spp. in Gujarat.
Family SYRPHIDAEThese are small to medium-sized flies that can hover motionless in the air.They visit flowers as bees and wasps.These flies feed on nectar and are major pollinators of some flowering plants in world over & in India.So far 46 species of hover flies have been reported as flower visitors and pollinators from India.Datta & Chakraborty (1983) reported 25 species from Jammu & Kashmir.Dhara Jothi & Tandon (1993) observed that there is no significant difference in pollinating activities of Eristalinus arvorum in between forenoon and afternoon on Zizyphus mauritiana.Mishra & Kumar (1993) reported hoverflies as one of the major pollinator groups of rapeseed and almond.Priti & Siahag Family TACHINIDAEThese are stout, medium to large sized flies, very bristly, particularly around the posterior of the abdomen.They are often grey with checkered patterns, but sometimes appear solid black or brown.The adults are nectar feeder and are the common visitors of many wildflowers.In India, only 3 species are reported as flower visitors.Bhatnagar (1986) reported their role in pollination of the family Asclepiadaceae.Family TEPHRITIDAEThe members of the family Tephritidae are commonly called as "fruit flies", although the majority of the world's species are not frugivorous.The adult tephritids typically rest on flowers, fruit or vegetation with flex wings and oviposit on the flower heads of the family Asteraceae.They are not well known pollinating group in India, only 3 species are reported as flower visitors.Bhatnagar( 1986) andMitra et al. (2004)  studied their Rec.zooz.Surv.India pollinating activities in India.REMARKS The present communication reports 116 species belonging to 16 families of Diptera along with their 92 visited plant species belonging to 39 families (Table-I).It is revealed that the family Syrphidae is the dominant group among the flower visiting flies of India (46 plant species) and the family Asteraceae (17 species) is the most favoured plant family by dipterans.

Table - !
: List of Flower visiting-flies along with their visited plant species