Gardening for flies 3 – adding filth

In my continued quest to attract subjects for my photography, I decided to try to attract the drone fly, Eristalis tenax, a relatively large flower fly that mimics honeybees. Their rat-tailed larvae are said to be found in extremely foul aquatic conditions, such as cesspools, and runoff from feedlots. Not wanting to deal with feces in attracting these flies, I decided to try just using plant material. I put in a few rotting peaches, some soil, and some mulch in a plastic container and filled about half full with water. I then let it sit for a month, keeping the water level up so that it didn’t dry out. A cautious sniff confirmed that I had replicated the high degree of foul stench that I was trying for. It was contained, however, in a small area, that didn’t affect the rest of the yard.

So far, no drone flies have been noted, but a different and equally interesting fly was attracted. This fly, commonly known as a “boatman fly” is a species classified in the family Platystomatidae. Its scientific name is Pogonortalis doclea, and like many denizens of the city, it is a non-native. Somehow it has arrived here from Australia and become naturalized to our city.

Its behavior is interesting: it constantly waives its wings, which are marked with distinctive patterns of black. This display is usually considered either a threat to other males, or a welcome to females. Whichever, these flies display all the time, as well as projecting their mouthparts in and out. Look at this video and you’ll see what I mean. Disgustingly, these flies feed on the foul water, and in you can see thousands of maggots writhing around it.

The filthy water also attracts other flies, including Megaselia scalaris, one of the most polyphagous (feeds on anything) of all the phorid flies. It is found around the world, having been successful at living wherever humans live.

I’ll keep my eye on the filth container, and see what else turns up. I still haven’t given up on the rat tailed maggots, which might show up next year when I increase the amount of filth.