Flies Falling to Fungi and Other Dipteran Observations

In my backyard, I usually see a lot of Flies of various species, many of which I find difficult to identify. Flies don’t have the obvious characters or colours that other Insect groups have such as Butterflies and Beetles. There are two broad divisions of the Order Diptera (that is, the True Flies) which can be fairly easily distinguished. Nematocera roughly translates as “long-horned”, referring to their relatively long antennae and includes the Midges, Mosquitoes, Fungus Gnats and many others. Brachycera means “short-horned” and includes the House Flies, Carrion Flies, Fruit Flies, and dozens of other massive groups. As I mentioned in my post about observations at my Parents’ house, I’m reading through Flies by Stephen Marshall and it’s only reinforcing the bewildering diversity of Flies and Insects in general.

Incidentally, a Fly that I can’t identify landed on the book Flies as I was reading it in my house. There is a Family of Flies called the Ironic Flies (Family Ironomyiidae), but unfortunately this definitely isn’t one of them. That would have just been too perfect. My best guess for this Fly is a Fungus Gnat or a related Family (Sciaroidea).

All that being said, there are some Flies that I can now identify on sight such as this Common Picture-Winged Fly (Delphinia picta):

Others easy to identify (to Genus) are the Condylostylus flies which hunt small prey and display on leaves worldwide. 

Another group of Flies that I’ve become familiar with have one of the most unsettling Family names ever: the Flesh Flies (Sarcophagidae). The three black stripes on the thorax distinguish them from similar-looking Flies (Marshall, 2012). To make them even more unappealing than their name, many of these Flies lay eggs that hatch immediately after they leave the female, or they simply lay larvae that have already hatched. There are about 3000 species in the Family Sarcophagidae, and the ones I see in my backyard are likely in the Genus Sarcophaga. Within the Genus Sarcophaga there are 800 species, so they are very difficult to generalize about, with some of their larvae feeding on or within other insects, consuming dead vertebrates, or specialist parasitoids of spider or grasshopper eggs (Marshall, 2012).

Another Fly observed within my own house is likely a member of the aptly named Window Fly Family (Scenopinidae), as I photographed it on the interior of my back door window. Although this Family of about 350 species is associated with various habits and habitats, they are named for the handful of species that are predators of human-habitat insects such as Carpet Beetles (Dermestidae), which is likely what my Window Fly was.

The most eye-opening Fly observation of the month has more to do with the fate of the Flies, rather than the Flies themselves. I found two Flies in my garden in a bizarre position, one at the very end of May and one on the 1^st of June. I’m unable to identify either species of Fly beyond the fact that they’re both Brachycerans. Each fly was positioned at the end of a leaf, clutching it with its legs and they were covered with what looked like white dewdrops bursting out of their bodies on tiny filaments. The filaments emerging from the fly bodies (the Flies were also quite dead or at least incredibly still and unresponsive) must have belonged to a type of Fungi.

Many readers may be familiar with the incredible footage in BBC’s Planet Earth of the Cordyceps fungus infecting ant workers and forcing them to climb into the tree canopy in order to release the fungal spores upon death. What might surprise you is that similar insect-infecting fungi are found not only in tropical rainforests but around the globe, even in my own backyard in Simcoe, Ontario. In fact, Cordyceps itself occurs in parts of North America (into the Southern United States), where it infects insects and causes similar scenarios to the one depicted in Planet Earth (Eiseman and Charney, 2010). There is an entire order of fungi, Entomophtorales, in which most species infect insects and other arthropods. If you’re interested in similar observations, there’s a Bugguide page devoted to this sort of thing. I have no idea which species infected these Flies in my backyard, but it’s fascinating to know that these sorts of complex interactions are occurring right where I live.

For previous June 2021 Observations, see:

–Fuzzy Flies and Song Sparrows

–The Wonders of Wrens

And for another post focused on a species of Diptera, see:

–Species Profile: Eastern Band-winged Hover Fly

References:

Eiseman, Charley and Charney, Noah. Tracks & Sign of Insects and Other Invertebrates: A Guide to North American Species. 2010.

Marshall, Stephen. Flies: The Natural History and Diversity of Diptera. 2012.