Flower Flies
Citation
Skevington, J.H. and Young, A.D. (2016). 6.18. Flower Flies. pp.152-157. In: Working Group on General Status of NWT Species. NWT Species 2016-2020 – General Status Ranks of Wild Species in the Northwest Territories, Department of Environment and Natural Resources, Government of the Northwest Territories, Yellowknife, NT. 304 pp.
Plain language summary
The Northwest Territories (NWT) is home to a diverse group
of plants and animals. About 30,000 species are estimated
to occur here. An important first step in safeguarding
biodiversity is to increase our knowledge of each species
and to provide a mechanism to monitor the conservation
status of each species regularly. Monitoring the status ranks
of species is important to detect changes before they
become critical and to determine which species need a
more detailed assessment or closer monitoring.
This report on the general status of wild species in the
NWT was produced collaboratively with other agencies
and wildlife co-management boards, and with the input
from many knowledgeable people from the NWT and
elsewhere.
General Status Ranks provided in the NWT Species 2016-
2020 report are valid from 2016 to 2020 inclusively.
The NWT Species 2016-2020 is the fourth report of the NWT
General Status Ranking Program. The reports are issued
every five years and species status ranks are valid for the
whole period. The current report provides ranks for 5,357
species, about 17% of all species expected to be present
in the NWT.
Over the past five years, one percent of status rank
changes can be attributed to an increase in threats
to species. These threats are complex and include the
effects of climate change and new diseases. Additional
groups of insects are ranked in this report and the results
of many years of new inventories in the Beaufort Sea are
yielding a rich database on marine biodiversity. Many
changes in ranks over the past five years were due to new
information. However, still not enough information was
available to rank the general status of most (52%) species.
Enthusiasm for biodiversity is encouraging. More people
are sharing information on species using social media,
often providing high-quality digital photographs of great
taxonomic value.
Abstract
The Syrphidae are known as hover flies, flower flies or
syrphids. This family is part of the Order Diptera, true flies.
True to their common names, most adult syrphids are
flower visitors as adults and some are among the most
adept fliers in the insect world, reminiscent of miniature
hummingbirds as they work flowers for their nectar rewards.
Flies in general contribute nearly 40% of our pollination
services and flower flies are the most important single
group of Diptera pollinators. Because flower flies are often
excellent mimics of bees and wasps (they are harmless
but gain protection from predators who mistake them for
stinging insects), they are commonly overlooked at flowers.
Indeed, many books, advertisements, media articles and
literature extolling the benefits of bees mistakenly illustrate
flower flies.
In contrast with the relatively uniform adult ecology of
syrphids, larval flower fly ecology is amongst the most
varied of any insect family. Larvae of one large subfamily
of flower flies, the Syrphinae, are mostly predatory on
aphids, scales and other insects. Many of these species
are of critical importance in controlling pest numbers. A
related subfamily, the Pipizinae, feed on specialized root
aphids whereas the bizarre ant flies (Microdontinae) are
predators and parasitoids of ants. From what we know
(only 8% of ant flies have known larval life histories), these
flies are typically host-specific and have evolved to mimic
the chemical communication systems (pheromones
and related) of their hosts. Ant fly larvae are thus able
to wander around in ant nests with impunity while they
feed on ant larvae and eggs. The other huge group of
flower flies, the Eristalinae, includes almost every larval life
history imaginable. There are predators here too, but the
majority filter bacteria from their surroundings in a wide
variety of ways. Some live in rot holes and are excellent
indicators of the health of old growth forest ecosystems,
some live in sap runs under bark, many live in ponds, rivers,
bogs, and other wetlands, and some live in putrid water
such as that found around farms or sewage lagoons
(this includes the familiar rat-tailed maggots). Species
that live in putrid water are often found in the billions
and are critical in improving water quality. These species
are being investigated for use on a commercial scale in
water treatment facilities. Other eristaline larvae are plant
feeders, with a few such as the bulb flies even achieving
pest status. Some species are very specialized, and leaf
feeding, stem feeding and root feeding species may cooccur
on the same plant without directly competing. There
are also a few specialized leaf miners, woodborers and
pollen feeders.
The most diverse genus of flower flies found in the NWT is
the Platycheirus (sedgesitters). Many of these flies have
fantastic modifications of the male legs. These speciesspecific
‘flags’ are used for sexual display. As the common
name implies, many sedgesitters are wetland specialists
and can often be seen sitting on sedges and possibly
feeding on sedge pollen.
So, syrphids are also extremely diverse. Over 6,200 species
have been described worldwide and we estimate that
8,000-10,000 exist. This single family of flies thus rivals the
diversity of birds on a global scale. In Canada, we have
discovered over 500 species and add new species
regularly as knowledge of them expands.