Other Pollinators — Flies
Flies are second only to bees in terms of importance for pollination. Flies have been documented
to be primary pollinators for many plant species, both wild and cultivated.
There are around 7,000 known species of flies but by comparison, there are about 250 species of bees.
Bees are often seen as the main insect pollinators and as they are certainly playing a very important role in
pollinating many plants we should not forget all the flies. Many flies will visit flowers for pollen and nectar
Flies have only one pair of wings; the second pair is converted into stalked knobs which are called halters.
Halters are balancing organs located just back of the base of the wings. Halters are used for balancing in flight.
Most adult flies have well-developed wings and fly readily and many of them are important
Hoverfly species, genus Syrphidae, poster
Flies usually feed on exposed fluids but can also eat small solid particles such as pollen grains. The taste organs
are mainly located near the mouth but flies can also taste with their legs (taste organs in the legs are located in the
tarsi, the end part of the legs). The legs of Blow flies (Calliphoridae) for example are 100-200 times more sensitive to
the taste of cane sugar (sucrose) than the human tongue. Some flies locate suitable flowers by following the
distinctive flower scent which they detect with their antennae. Most flower-visiting flies also have large eyes and at
least the higher developed flies have color vision which helps with finding flowers from afar.
Flowers are not only places to find nectar and pollen but are also used by some flies as a place to find a mate, to lay
their eggs or to take shelter.
In contrast to many bees, flies still fly in less favorable weather conditions and on cold, windy and overcast days
flies are often the only flower visitors you will see. Plants growing in damp, shady places such as woodlands would
struggle to attract bees but flies are often abundant in these places and quite a lot of woodland plants get pollinated
by flies and not by bees.
The flowers that are pollinated by flies are typically:
Pale and dull to dark brown or purple
Sometimes flecked with translucent patches
Putrid order, like rotting meat , carrion, dung, humus, sap and blood
Nectar guides not present
Flowers are funnel like or complex traps
Flies (Diptera) can be split into two main groups, the Nematocera and the Brachycera. Nematocera have elongated
bodies and long, often feathery antennae. Midges, mosquitos and crane flies belong to this group. Brachycera have
a more roundly proportioned body and short antennae and all the remaining flies such as hoverflies (Syrphidae),
house flies (Muscidae), blow flies (Calliphoridae) and flesh flies (Sarcophagidae) belong to this latter group.
An important group of flower-visiting flies are the root-maggot flies (Anthomyiidae), house flies (Muscidae) and
Fanniidae (no common name). All are relatively small grey flies and they like to visit sweet-scented flowers. They
also seem attracted to sweet-scented flowers with a tang of stale dung or urine smell.
Other flies commonly found on flowers are the blow flies (Calliphoridae) which are often metallic green or blue in
color and the large grey flesh flies (Sarcophagidae). Both can also be found feeding on carrion and excrement but
will often visit flowers to feed on the nectar.
Dung flies (Scathophagidae) are predatory flies and often visit flowers to seek out prey. But many dung flies will also
feed on the pollen and nectar of the flower.
Hoverflies or Syrphid Flies (Syrphidae) are the most important family of flower visitors among flies. There are over 270
species of Syrphid Flies are commonly brightly colored with yellow and black or red and black
bodies. Many of the darker colored species often look highly polished and some hoverflies are very furry
and resemble bumblebees.
Many Syrphid Flies can be seen visiting flowers in sunny places but there are
also quite a lot of species living in damp shady woodlands or at the woodland edge. Syrphid Flies get their
name from the ability to remain stationary in the air which makes them easy to distinguish from wasps or
bees. Most Syrphid Flies visit flowers for nectar but some are specialized pollen feeders and often
visit flowers just to feed on the pollen.