Backyard Hover Flies

Sweat Bee

One flower that does really well in my garden in the late summer is the aster. I purchased a plant from a local nursery a few years ago, and although I don’t remember which type it is, every year it comes back and produces a bounty of small, purple flowers. It has spread over the years, turning my back garden into an untidy mess of green and purple each September; and this year I even noticed a few plants growing in my lawn!

Asters provide a wonderful source of pollen and nectar in the early autumn when few plants are flowering. In fact, the nectar provided by late-blooming flowers helps to ensure that bee colonies are strong enough to endure the winter. Other insects that benefit from the asters are beetles, butterflies, moths, wasps, hover flies, and sweat bees, such as the one shown to the right. I usually spend some time checking out the various visitors on the flowers each autumn, but for some reason this year I never made the time. Then one day just after the September equinox I happened to notice a large number of insects buzzing around the flowers when I came home from work. I went out with my camera to have a look and was surprised by the bugs that I found!

There were a few bumblebees and metallic green “Greenbottle” (Lucilia sp.) flies present, but it was the hover flies that interested me. These bee and wasp mimics are usually patterned with black and yellow stripes, and have a tendency to hover in one spot with their wings beating so fast they become invisible. They have only one pair of wings and short, stubby antennae which helps distinguish them from bees and wasps. They range in size from large to small, and this one was so big that I thought it was a wasp at first. I almost ignored it while concentrating on the smaller hover flies; luckily I decided to take a few pictures, as it is a hover fly I’ve never seen before!

Hover fly (Spilomyia longicornis)

According to Bugguide.net, these hover flies can be found between September and November in North America at low elevations. They mimic Polistes or Yellowjacket wasps with their black and yellow-striped abdomen and pigmented eyes, though the eyes remind me more of deer flies than wasps.

Hover fly (Spilomyia longicornis)

This Helophilus species is another large hover fly, and a much more common one than Spilomyia longicornis (unfortunately hover flies do not have common names….yet). I see them throughout the warmer months, but this is the first time I’ve seen one in my yard. The vertical stripes of thorax contrast with the horizontal stripes of the abdomen with a gold-coloured scutellum in between.

Hover fly (Helophilus sp.)

Another photo of the same individual:

Hover fly (Helophilus sp.)

Toxomerus geminatus just may be the smallest hover fly I’ve ever seen and, as a result, is one of the most difficult to photograph. I see them frequently in my garden. They can be separated from the similar-looking Toxomerus marginatus by the lack of a yellow margin on the abdomen and a blackish scutellum with a well-defined U-shaped yellow margin.

Hover fly (Toxomerus geminatus)

Not all of the hover flies that I saw were so easily named. In fact, some hover flies are so difficult to identify without macro photos showing every angle that it may not be possible to even narrow it down to the correct genus. Without a proper field guide on hover flies, or flower flies as they are also known, it’s difficult to even know where to begin. Many can only be referred to simply as Syrphid flies.

This Syrphid fly is a new one to me. I didn’t get great photos of it the first time, and although I went back for more photos the following two days, I didn’t see it again. [Author’s update – January 2016: this species has since been identified as Oblique-banded Pond Fly (Sericomyia chrysotoxoides) by Dr. Jeff Skevington, who is working on the field guide to the Syrphid Flies of Ontario mentioned below.]

Oblique-banded Pond Fly (Sericomyia chrysotoxoides)

Although I am not sure of the species, I’ve seen this type of hover fly before. It appears to be common in Ottawa as well.

Syrphus sp. – identified by Jeff Skevingon in January 2016

Here is another one, similar to the above. I was able to get out on the weekend when the sun was still shining on my back garden.

Syrphid sp.

This looks like another new hover fly for me. The bright red eyes really stood out; I spent a lot of time following him around!  [Author’s Update: this one has been identified as Transverse-banded Drone Fly (Eristalis transversa) by Dr. Skevington.]

Transverse-banded Drone Fly (Eristalis transversa)

And yet a different species I’ve never seen before. This fellow was also around for just the one day.  [Author’s Update: this one has been identified as American Thintail Meliscaeva cinctella) by Dr. Skevington.]

American Thintail (Meliscaeva cinctella)

Although this one doesn’t resemble the other hover flies, it caught my attention by its distinct hovering and darting motions, so I spent some time following it around as well. Unfortunately it liked to perch with its wings folded over its back, so the pattern on the thorax isn’t clear. However, the greatly enlarged femur, and the black and red markings on the legs pointed to Syritta pipiens, a common species often found feeding on flowers.

Syritta pipiens

For anyone interested in these small but fascinating flies, the Canadian National Collection (CNC) of Insects, Arachnids and Nematodes is currently working on a field guide to the Syrphidae of Northeastern North America. It also has an online field guide for species found in Ontario, though it isn’t helpful if you don’t know how to identify the various genera (singular: genus), as I don’t. Hopefully the book form will have more details on what makes each genus unique, and what to look for when you see a new Syrphid fly.

Although not a pollinator, I found this Two-spotted Stinkbug among the asters as well. I’ve seen these in my garden previously, back in June 2011 when they found the columbines to their liking. This one is missing part of its antenna:

Two-spotted stinkbug (Cosmopepla sp.)

There were also several bumblebees, a wasp, and a single sweat bee feeding on the flowers. Although I was thinking about and redesigning my back garden and getting rid of the asters, I’m hesitant now after seeing how many insects depend on them for food. They are an important component of any wildlife garden and attract not just bees, but also hover flies which are also beneficial as they feed on aphids!

Advertisement