{{Short description|Species of fly}} {{Speciesbox | image = Narcissus bulb fly (Merodon equestris) grooming.jpg | image_caption = Grooming | range_map= Merodon_equestris_map.png | range_map_caption= Distribution map | status = LC | status_system = IUCN3.1 | status_ref = <ref name="iucn">{{cite iucn |author= Veselić, S. & Radenković |title=''Merodon equestris'' |year=2021 |article-number=e.T149168430A149168435 |doi=10.2305/IUCN.UK.2021-3.RLTS.T149168430A149168435.en |access-date=21 October 2022}}</ref> | genus = Merodon | species = equestris | authority = (Fabricius, 1794) | synonyms = *''Eristalis narcissi'' <small>Fabricius, 1805</small> *''Merodon narcissi'' <small>(Fabricius, 1805)</small> *''Merodon transversalis'' <small>Meigen, 1822</small> *''Merodon validus'' <small>Wiedemann, 1822</small> *''Syrphus equestris'' <small>Fabricius, 1794</small> }}

'''''Merodon equestris''''' (Narcissus bulb fly, greater bulb fly, large bulb fly, large Narcissus fly)<ref>{{cite web|url=http://www.bugsandweeds.co.uk/hoverflies.html|title=Hoverflies|access-date=2009-12-12}}</ref> is a Holarctic species of hoverfly (Family Syrphidae).<ref name="Stubbs">{{cite book|author1=Stubbs, Alan E. |author2=Falk, Steven J. |name-list-style=amp |year=1983 |title=British Hoverflies: An Illustrated Identification Guide|pages=253, xvpp |publisher=British Entomological & Natural History Society}}</ref><ref>Van Veen, M. (2004) ''Hoverflies of Northwest Europe: identification keys to the Syrphidae.'' 256pp. KNNV Publishing, Utrecht.[http://home.hccnet.nl/mp.van.veen/syrphidae/boekhoverflies.html addendum]</ref><ref>Van der Goot, V.S. (1981) ''De zweefvliegen van Noordwest - Europa en Europees Rusland, in het bijzonder van de Benelux''. KNNV, Uitgave no.32: 275pp. Amsterdam.</ref> <ref>Bei-Bienko, G.Y. & Steyskal, G.C. (1988) ''Keys to the Insects of the European Part of the USSR'', Volume V: Diptera and Siphonaptera, Part I. Amerind Publishing Co., New Delhi. {{ISBN|81-205-0080-6}}.</ref><ref>Coe, R.L. (1953) Diptera: Syrphidae. ''Handbks.ident.Br.insects,'' 10(1): 1-98. R.ent.Soc.London. [http://www.royensoc.co.uk/sites/default/files/Vol10_Part01.pdf pdf]</ref><ref>Peck, L.V. (1988) Syrphidae. In: Soos, A. & Papp, L. (eds.) ''Catalogue of Palaearctic Diptera'', 8: 11-230. Akad.Kiado, Budapest.</ref> Like many other hoverflies it displays a colouration pattern similar to a stinging insect (a bumblebee in this case) as an evolutionary defense mechanism. Other syrphid bee mimics are ''Mallota'', ''Arctophila'', ''Criorhina'', ''Pocota'' and ''Brachypalpus''. ''Merodon'' species are distinguished from these by the very strong hind femora, which bear a large triangular projection on the underside near the tip. It flies in low vegetation while the other bumblebee mimics prefer higher vegetation layers.

==Description== A stout fly with a small head (10–14&nbsp;mm in length).<ref name=":0">{{Cite book |last=V. Evans |first=Arthur |title=National Wildlife Federation Field Guide to Insects and Spiders of North America |publisher=Andrew Stewart Publishing, Inc |year=2008 |isbn=978 1 4027 4153 1 |page=243}}</ref> The tergites are black, without the dust spots or blue-purple sheen of other ''Merodon'' species. The thorax and abdomen are hidden by dense, long, erect hairs of variable colouration. Tibia 3 of the male has 2 spurs at the apex.<ref>Bradescu, V. (1991) Les Syrphides de Roumanie (Diptera, Syrphidae), Clés de détermination et répartition. ''Trav.Mus.Hist. nat. Grigore Antipa'', 31: 7-83.</ref> The larva is described and figured by Hodson (1932) <ref>Hodson, W.E.H. (1932) The large narcissus fly, Merodon equestris, Fab. (Syrphidae). ''Bull.Ent.Res''., 23: 429-448</ref> and it is illustrated in colour by Rotheray (1993).<ref>Rotheray G., 1993 ''Colour Guide to Hoverfly Larvae Diptera, Syrphidae in Britain and Europe'' Dipterists Forum [http://www.dipteristsforum.org.uk/documents/DD/df_1_9_Colour_Guide_to%20Hoverfly_Larvae.pdf pdf]</ref> Males have eyes clearly touching at the front, while in females these are separated by a (yellow haired) antenna like structure at the front.

==Distribution== In the Palearctic it is found from Fennoscandia south to Iberia and the Mediterranean basin, and Ireland east through Europe into Russia and Japan. In the Nearctic it is found from British Columbia south to California. It has been introduced to New Zealand. (see map) <ref name="Speight"/>

==Biology== They inhabit open areas in deciduous forest up into the subalpine zone but significantly synanthropic, occurring in suburban parks and gardens and on horticultural land.<ref name="Speight">{{cite journal | last = Speight | first = M.C.D. | year = 2011 | title = Species accounts of European Syrphidae (Diptera)| journal = Syrph the Net, the Database of European Syrphidae | volume = 65 | pages = 285pp | url= http://www.diptera.info/downloads/StN_Species_Accounts_Glasgow_2011.pdf }}</ref> The adult flies low in April to July with a fast zig-zag flight, among ground vegetation frequently settling on bare ground. Adult ''M. equestris'' feed on pollen and nectar. They visit a large variety of flowers for nectar,<ref>de Buck, N. (1990) Bloembezoek en bestuivingsecologie van Zweefvliegen (Diptera, Syrphidae) in het bijzonder voor elgië. ''Doc.Trav.'' IRSNB, no.60, 1-167.</ref> while the larvae feed internally in tissues of bulbs of Amaryllidaceae, and they are regarded as a horticultural pest, especially of ''Narcissus''. Females lay 1 egg at a time on leaves of this plant (or in soil by it). Larvae overwinter in the bulbs.<ref name=":0" /> A bibliography of the literature on the biology of ''M. equestris'' is given by Barkemeyer (1994).<ref>Barkemeyer, W. (1994) Untersuchung zum Vorkommen der Schwebfliegen in Niedersachsen und Bremen (Diptera: Syrphidae). ''Naturschutz und Landschaftspflege in Niedersachsen'', 31: 1-514.</ref>

==Colour forms== <gallery> File:Merodon (female).jpg|var. equestris (female) File:Merodon equestris (male).jpg|var. narcissi (male) File:Merodon equestris01.jpg|var. validus (female) </gallery>

==References== {{Reflist}}

==External links== {{Commons category-inline|Merodon equestris|''Merodon equestris''}}

{{Taxonbar|from=Q1760952}}

{{DEFAULTSORT:Merodon Equestris}} Category:Eumerini Category:Flies of Asia Category:Flies of Europe Category:Flies of North America Category:Hoverflies of North America Category:Insects described in 1794 Category:Taxa named by Johan Christian Fabricius Category:Flies of New Zealand