162 THE ESSEX NATURALIST
species prey on green-fly; and adult flies visiting flowers (particu-
larly white and yellow ones) for pollen and nectar are active agents
in pollination, playing perhaps an even larger part than bees
because of their greater numbers. Although some of the furry
hover-flies have a close superficial resemblance to bumble-bees,
and others resemble honey-bees or even wasps, they are of course
members of the order Diptera, of which they constitute one of the
most distinctive and easily recognised families. Like all Diptera,
they differ from other flying insects in having only one pair of
wings. Observation will also show that their flight is quite
different from that of bees and wasps, being much more sudden,
rapid and direct.
The entomologist can study hover-flies without ever leaving his
back garden, however restricted in size this may be. Indeed, I
found that my very small garden at Loughton provided me over
the years with almost as many species as Epping Forest itself. The
notable exception was the genus Cheilosia, of which I found
several more species in the Forest than in my garden : this may
reflect the more specialised habitats (plant stems and fungi) re-
quired by the immature stages of flies of this genus.
During the nine years in which I pursued the flies of Essex
(1958-1966) I made no sustained efforts to collect hover-flies—my
main interest lay elsewhere in the Diptera. But it may be worth
putting on record the species noticed in my garden, particularly
since there appears to be no hitherto published list of flies of this
group observed in a small suburban plot.
The garden (of under 300 sq. yards—270 sq. m) contained no
special features other than a small artificial pond, though its
proximity to Epping Forest may have been responsible for the
occurrence of a few species not normally associated with gardens.
It must be remembered that almost all hover-flies are powerful
fliers capable of covering considerable distances in their search
for food. Some of the larger species indeed are known migrants,
for example Scaeva pyrastri, which occurred at Loughton only in
certain years.
The list of species follows. Nomenclature is that of the widely-
used key by R. L. Coe (1953). My observations of these flies were
not systematic enough to warrant the publication of either fre-
quency or dates of appearance.
Baccha obscuripennis Mg.
Platychirus manicatus Mg.
P. peltatus Mg.
P. scutatus Mg.
P. albimanus F.
P. clypeatus Mg.
P. angustatus Zett.
Melanostoma ambiguum Fln.
M. scalare F.
Sphaerophoria scripta L.
Syrphus balteatus Degeer
Rhingia campestris Mg.
Neoascia podagrica F.
Pipiza luteitarsis Zett.
P. bimaculata Mg.
Cheilosia albitarsis Mg.
Volucella inanis L.
V. pellucens L.
Eristalis pertinax Scop.
E. tenax L.