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					Hover Flies ( known in America as Flower Flies ) belong to a large family of small to big flies. They are true flies
or Diptera, with only one pair of wings in the Family Syrphidae. ( Wasps and bees have two pairs ).

Hoverflies have spots, bands or stripes, of yellow, brown against a dark-coloured background, sometimes with
dense hair covering the body surface (emulating furry bumble bees). Their fast flight, motionless flight and, in
some species, their size are astonishing feats. Some Hovers are among the biggest flies of Central Europe.
Many species are very colorful. It is not always that easy to identify hover flies. Some thick-headed flies and
bee flies are similar and dark coloration makes it hard to identify them correctly at a glance. Bee flies tend to
be longer hairy, have snouts and are a study in themselves!

Hovering is a speciality although other flies can also hover - the head of the insect remains absolutely still
whilst in flight. They may be seen "Nectaring" on many wild and garden flowers where they are amongst the
most frquent of visitors. In Holland and Belgium alone over 300 species exist!. In Britain About 270 species are
known at present, but significant species and numbers can migrate like butterflies with powerful flight such as
the Red admiral or Painted lady.The Marmalade Fly Episyrphus balteatus is one of the most common hoverflies
to be seen in the garden. The distinctive double stripes on the abdomen make it almost unmistakable.

Many are seen in the summer season in number mixing with butterflies, bees, bumble bees and other flower
dependent insects. Male Hovers tend to enmerege and mature first, earlier in the season to ensure
reproduction is sucessful. Many species are useful to the gardener since their larvae eat pest aphids on garden
plants and crops.The degree to which they contribute to pollination is also ironically poorly investigated but no
doubt are important for Carrot, Onion and fruit Trees.

This group is a useful indicator for evaluating site ecology, being a day active, with a varied range of larval
habitat specialisations

What is the purpose of the Bright bodies and patterns?

Many of the of hoverflies have ornate body patterns, often of black and yellow, to
mimic wasps and bees but are harmless. Hover fly mimicry include warning
coloration of yellow and black, a narrow waist like a wasp and even the ability to
mimic the stinging action of a wasp, by pushing the tip of the abdomen into your
fingers if they are caught and held.

The superficial resemblances (a) to honeybees (for example the genus Eristalis
spp ), to (b) bumblebees (in the genera Pocota or Volucella) and to (c) wasps (in
the genus Chrysotoxum) is often striking.



  Fig 1 The Drone Fly Eristalis tenax (Left) & Honey Bee - Apis melifera (Right)
                          feeding on everlasting Daisy
                     IMAGE WITH THANKS YVONNE (C) 2007

Fig 2. The Common Wasp ( paravespula vulgris ) Left compared to the Hover Fly
                   Right (Chrysotoxum cautum - female)
               IMAGES (C) COLIN DUKE 2007 (C) DAVID ILIFF 2007

Fig 3. The Bumblebee (Bombus ) Below Left compared to the Hover Fly Below
                       Right (Volucella bombylans)
                 IMAGES (C) COLIN DUKE 2007 (C) LEON TRUSCOTT2007

Comments

(a) In the Eristalis species there are more subtle varieties as they attempt to emulate
the various form the honey bee takes Merodon equestris var naricisus, var
equestris. There is some evidence to suggest that colour form depends on
temperature exposure that larvae experience, with lighter forms appearing mid-
summer and darker forms earlier in the year.

(b) Volucella bombylans var plumata imitates the Earth or Common garden
Bumblebee. The Hover Fly larva of this species go one step further and actually
live in the nests of bumble bees, eating the rubbish produced being both
detritivores and larval predators. and possibly the bees larvae as well.( exception is
V. inflata who live in aqueous insect messes)

(c) The genus Chrysotoxum admirable displays associated features,wasp like
stripings, dark wings, resembling social wasps the antennae are long and wasp like,
not seen in typically in many other flies. Fig 2. Another good but less common
example is Doros profuges, a large hoverfly, the adult of which is a spectacular
wasp-mimic

Some species wave their front legs in front of their face to mimic the jointed
antennae of the potter wasps. It is thought that this mimicry protects hover flies
from falling prey to birds and other insectivores which avoid eating true wasps
because of their sting. Hover flies do not sting and are harmless.

This kind of Mimicry is know as Batesian mimicry involving a palatable,
unprotected species (the mimic - Hoverfly ) that closely resembles an unpalatable
or protected species (the model - The Bee or Wasp ). Birds know not to attack a
bee as they will be stung. Gilbert (2004) Ref 11further extends that Hoverflies also
behaviourially mimic the patterns and habits of their hymenopteran models.

Clearly Hoverflies not only mimic the host but have developed elaborate
evolutionary mechanisms to ensure the larva survive

What is the easy way to confirm if a Fly is a Hover?

Much information can be revealed by the wings - two in the case of Hoverflies as
oposed to 4 in the Mimic - The Bees

Despite the rather random appearance of veination in hover flies a logical appraisal
of characteristics can be applied based on veins that radiate outward - Radial veins,
Median Veins and Anal Veins. The distinctive presence of the two cross veins in
the Hover flies are described below.

Like many diptera looking at veination characteristics takes identification one
stage further. To confirm an insect is a Hover one of the most characteristic
features of hoverflies is the presence of a longitudinal false vein in the wing if an
examination of wing veins is necessary. In Hovers a great part of the edge of the
wing is without veins. The vein running all the way to the edge in most flies (
Radial), only reaches the last transverse vein, not the edge in hover flies upper
outer cross vein (A) and lower outer cross vein. Another feature of hover flies is
the so-calles 'floating vein' (B). This vein just ends nowhere. Usually veins end
either at the edge of the wing or in another vein. Both these features being present
means you are actually looking at a hover fly.
Generally the dorsal thorax does not have coarse bristles.

Looking at the behaviour of the Fly in air also confirms that it is a hover either by
its characteristic controlled hovering or its rapid start stop darting.

            Fig 4 Veination in the Hover Fly - the false or floating vein.




How Do I begin to identify the many Species?

Becoming familiar with Hoverfly Antomy will soon yield subtle features used to
distinguish the many similar flies down to species as well as genera level. Using
Keys will readily assist..It is beyond the scope of this article to list or describe the
identification features in detail but the presence shape, size and colour of Bands
and/or Bars, Presence or absence of hairs on anatomical parts, banding on the eyes
are imoportant characteristics. Whether for example the Antenna is long,
short,elongated or the Arista is Plumose (feathered) Colour of hairs on
the Scutellum. The colour and shape of the face ( Flat Convex etc ). The angle of
which the eyes are set to the frons and the relative positioning of the occelli to the
front or rear on the head. Considerable attention is given to the "Veination" or
pattens of veins on the wings

Gilbert Ref: 4 is an excellent intoduction to basic Hoverfly Identification. As
expertise progressess the definitive works of Stubbs Ref: 1 is invaluable in
narrowing down each species using the many keys available. The identification of
Hoverfly Larvae in itself a study can be explored using an excellent guide on The
Hoverfly Larva by Rotheray Ref: 5. The amateur naturalist may make very
valuable contributions with report on for example distribution valuable to
the Hover Fly Recording scheme Ref 5

                      Fig 5:Basic Features of The Hover Fly
Glossary

Abdomen The last of 3 major components making up an insect containing
digestive organs etc

Alula A memmbranous flap close to the squama

Antenna Composed of 3 segments with a hair like projection - the arista arising
out of the third or final segment.

Arista - A bristle like structure arising out of the 3 segmented parts making up the
antenna

Frons - The space behind the antenna between the eyes when viewed dorsally.

Haltere - Balance organs located to the mid thorax which act as a "gyroscope" to
control flight.

Humerii - The raised corners to the front of the dorasal thorax

Ocelli - An arrangement of simple celled eyes usually in 3, on the top of head in a
triangulated vertex.

Occiput The margin immediately behine the Compounbd Eyes

Postalar Cali - Elongated swellings at the posterior corners of the Thorax.

Pre Genital Segment. The end segment located just below the 4th Tergite
containaining the genitalia
Plumose - Feathered like

Scutellum - Plate like structure between the abdomen and the thorax when viewed
from above

Spiracle - (Anterior,Posterior) Breathing pores located on the side of the thorax
toward the head and abdomen respectfully

Squama - where the hind margin of the wing meets the thorax there is a
membranous flange known as squama

Sternites - The ventral part of the abomen of which is segmented into 4 sternites

Stigma A small cell portion arising on the outer coastal margin on tghe forewing
which may not be transparent or in fact coloured

Tergites - The dorsal part of the abomen of which is segmented into 4 Tergites

Thorax - The portion between the head and Abdomen The second of 3 major
components making an insect containing respiratory organs etc



Where do they complete their Life - Cycle?

Like other flies Hovers go through all stages of insect life: egg-larva-pupa-imago.
The larvae of hoverflies are remarkably diverse for just one family of flies.

Some have adapted to aquatic life live in extremely dirty water (including stale),
eating all kinds of decaying materials. In order to breathe they developed a long
pipe at the rear end of the body, which they stick into the air. including the rat-
tailed maggots (about 40 species).

Other larvae hunt for plant lice or aphids. Over one third of hoverflies have larvae
that eat aphids (over 110 species).

Some live in decaying wood, or sap runs on live trees (33 species).

Some are a pest in agriculture eating live plant tissue such as roots, stems and
flower bulbs from within or as leaf miners (about 30 species).

Like the Large Blue Butterfly, The larva of the Hoverfly, Doros profuges, is
believed to live within nests of the ant Lasius fuliginosus. Little is known but one
assumption is larva must either feed upon root aphids that have been herded by the
ants or gain some other benefit from living within their nest.
There is much to learn and contribute about the life cycles of this interesting group
with many species very poorly documented or understood.

                      Fig 6: The Life Cycle of The Hover Fly




What do they Eat?

Adults

Adults feed mainly on nectar and pollen, beside nectar, Hover Flies feed on honey
dew produced by aphids as well. Hover Flies are one of the few kinds of insects
that can digest pollen, which is protein rich development of the eggs. The surface
coat of Pollen has is resistant to most insect digestive juices. The yellow
patternation can reflect the amount and type of pollen the insects have eaten, they
are often seen hovering or nectaring at flowers, while the larvae (maggots) eat a
wide range of foods.

Larvae

In some species, the larvae are saprotrophs, eating decaying plant and animal
matter in the soil or in ponds and streams. For example the rat-tailed maggot, larva
of the Drone fly Eristalis tenax is found in polluted pools and sewage. They
obtain air by extending their snorkel like tail breathing tubes to reach the water
surface.breaking it with feathery hairs which emerge from the tube Adults are so
called because of the resemblance to Drones of bees.

        Fig 7: The Larvae of the Drone Fly - Aka " the rat Tailed Maggot




                                                                                 .



Larvae may feed externally on plants or they may be internal feeders, attacking the
bulbs; for example the Narcissus Fly, Merodon equestris. also known as the Great
BulbFly . In other species, the larvae are insectivores and prey on aphids, thrips,
and other plant-sucking insects.

                    Fig 8: Hover Fly Larvae Grazing on aphids
Sexing Hover Flies

Like many other flies males and females often look alike, having the same
coloring, size etc. Exceptions are found especially among the drone flies, where
females differ from the males. However it's always easy to tell males and females
apart. Like all other flies the males have much bigger eyes. These eyes almost
touch each other in the middle and are therefore closer together. Females have
much smaller eyes, placed farther apart. Tiny eyes or occeli are composed of
simple cells and are found at the top of the head in a triangle between the large
compound eyes, perhaps this is why it is sometimes easier to get "underneath a
Hover fly when it hovers. ( t he nature/ physics and of eyes in the Male also
influences flight behaviour with males more able to judge distances and predate
females )

A more obtrusiive method of identifying the sex of the species is to look at the
underside of the abdomen, males have curbed asymetricla genitalia. The abdomen
of the female is more pointed with inconspicuous genitalia.

             Fig 9 Male Eye Form (Top) Female Eye Form (Bottom)




 Fig 10: Viewed from above Female Eye Form (Left) Male eye Form (Right). The
                              dotted triangle

          is composed of three simple eyes or ocelli the ocellar triangle.
Hover Habitats

Hoverflies indulge in a wide range of habitats many of which are in decline. The
favoured habitat for adult Doros profuges appears to be the transition zone between
woodland or scrub and calcareous grassland. but clearly this hoverfly is dependent
on its host the ant and factors which affect it such as the ants Northerly limit.
woodland and Forest management also play crucial with much dead and rotting
wood being removed.

The Golden Hoverfly Callicera spinolae is a large, colourful, hairy hoverfly that is
also at risk, adults can be found feeding from Ivy flowers in autumn. It is found
mainly in East Angli. The larvae live in rot holes in trees. Golden hoverflies are
saproxylic, they are dependent on decaying wood.

Other species include Aspen Hoverfly, Hammerschmidtia ferruginea which lives
in open aspen woodland in the Highlands of Scotland and depend on decaying oily
layers in Aspen and the Pine Hover Fly, Blera fallax.

Aquatic habitats such as bog give rise to distinctive fauna. The Bog
Hoverfly Eristalis cryptarum, a bee mimic also may be in decline due to the
disappearance of Boggy habitat. Bog Hoverflies have been seen nectaring on
marsh plants such as the flowers of bogbean, marsh marigold and cuckoo flower.

Hover Enemies
Hoverflies generally have no major "enemies aside perhaps opportunistic Spiders
and Birds. Based on observations of a tame Spotted Fly Catcher, Davies (1977)
notes that this mimicry does not fool it - the ability for this bird to distinguish
between Bees an the less conspicuous black and yellow Syrrphinae, rubbing off
stings in Bees but readily eating the hovers with no such precaution. However no
species is generally without an enemy some where in the food chain.Species of
solitary wasps ( Ectemnius cavifrons) specialise in taking hovers, social wasps will
also take Hoverflies in summers of when numbers are high. The hoverfly
parasitoid Wasp, Diplazon laetatorius, an Ichneumon Wasp, in the field, can
attack, and eventually kill, over half of all aphid-eating hoverfly larvae. Failing
behavioural responses the Hover Larvae may develop an immune response
deterring up to 1/5 of such attacks in for example the Marmalade Fly, Episyrphus
balteatus, due to host immunity. The parasitoid egg is surrounded by specialised
blood cells which release poisonous compounds that kill the invader. Nevertheless
many Hovers may readily fall prey to an even more insidious fate such as the
insect "eating" fungal infection.


                         COMMON BRITISH HOVER FLIES




              Marmalade Fly
                                                            Sun Fly
           Episyrphus balteatus
                                                      Heliophilus pendulas
           (C) Colin Duke 2006
                                                      (C) Colin Duke 2006
 Eristalix pertenax.   Melascaeava cinctella.

(C) Colin Duke 2006    (C) Colin Duke 2006
        Sericomyia silentis.
                                            Portevinia maculata
With Thanks (C) Leon Truscott 2007
                                     With Thanks (C) Leon Truscott 2007




       Ferdinandea cuprea.                  Melanostoma scalare.

With Thanks (C) Leon Truscott 2007   With Thanks (C) Chris Webster 2007
         Xylota sylvarum.
                                          Parasyrphus punctulatus
With Thanks (C) Leon Truscott 2007
                                     With Thanks (C) Leon Truscott 2007
                                           Epistrophe grossulariae.
        Epistrophe eligans.
                                     With Thanks (C) Leon Truscott 2007
With Thanks (C) Leon Truscott 2007




                                          Epistrophe melanostoma.

                                     With Thanks (C) Chris Webster 2007
            Myothropa florea

        Image (C) Colin Duke 2006




v




                                                 Dasysyrphus tricintum
         Dasysyrphus albostriatus.
                                         Image Copyright (C) Colin Duke 2007 All
    With Thanks (C) Leon Truscott 2007
                                                     Rights Reseved
       Merodon equestris.

With Thanks (C) Leon Truscott 2007
       Volucella pellucens.                 Volucella bombylans.

With Thanks (C) Leon Truscott 2007   With Thanks (C) Leon Truscott 2007
         Volucella inflata.

With Thanks (C) Chris Webster 2007           Melangyna cincta.

                                     With Thanks (C) Chris Webster 2007
                                          Melangyna umbellatarum
    Melangyna lasiophthalma.
                                     With Thanks (C) Leon Truscott 2007
With Thanks (C) Leon Truscott 2007




      Eupeodes latifasciatus.              Eupeodes latifasciatus.

With Thanks (C) Chris Webster 2007   With Thanks (C) Leon Truscott 2007
        Eupeodes luniger.
                                             Eupeodes luniger.
With Thanks (C) Leon Truscott 2007
                                     With Thanks (C) Chris Webster 2007
                                            Anasimyia contracta.
       Anasimyia contracta.
                                     With Thanks (C) Leon Truscott 2007
With Thanks (C) Chris Webster 2007
        Anasimyia lineata.                    Scaeva pyrastri.

With Thanks (C) Leon Truscott 2007   With Thanks (C) Leon Truscott 2007
       Leucozona lucorum
                                              Leuconza glauca
With Thanks (C) Leon Truscott 2007
                                            (C) Colin Duke 2006




   Chrysotoxum cautum female                 Cheilosia illustrata.

 With Thanks (C) David Iliff 2007    With Thanks (C) Leon Truscott 2007
                                          Platycheirus fulviventris.
      Brachypalpoides lentus.
                                     With Thanks (C) Chris Webster 2007
With Thanks (C) Leon Truscott 2007




      Sphaerophoria scripta.                 Rhingia campestris.

    Image (C) Colin Duke 2006        With Thanks (C) Chris Webster 2007
Table 1 General Classification of the Family: Syphidae
Sub-Family: Syriphinae
Genera
            Tribe Syrphini Eg Syrphus, Epistophe,
            Scaevia
            Tribe Bacchini Eg Bacchus, Melastoma,
            Platycheirus
Sub-Family: Eristalinae

Genera
            Tribe Cheilosiini Eg: Ferdinandea,
            Rhingia, Cheilosa
            Tribe Chrysogasterini Eg: Chrysogaster,
            Neoascia
            Tribe Volucellini Eg Volucella
            Tribe Sericomyiini Eg Sericomyia
            Tribe Xylotini Eg Syrittia, Xylota
            Tribe Eumerini Eg Merodon
            Tribe Eristinali Eg Eristais, Helophilus,
            Myiatropa
Sub-Family: Microdontinae

Genera

             Rare in UK

				
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