A golden mimic or how to stay alive by pretending to be something you’re not

My last post featured Eastern phoebes raising their young on our front porch. In that post I mentioned that Phoebes are flycatchers who make a living snatching flying insects out of the air. Today, I’m going to share a very cool recent sighting here at Pokeberry Pines that just so happens to have a connection to those Eastern phoebes…

My first sheet mulch experiment…

A few days after building my first sheet mulch bed last week, I noticed a new and charismatic visitor crawling and flitting around the newly rotting sheet mulch. It was big, and its iridescent purple/black wings caught my eye. I watched it for a few minutes and noticed that as it crawled around on the straw it curled its abdomen under, as if it was stinging like a wasp might or laying eggs like a butterfly. Curious, I got as close as I could and saw that it had large eyes, long, clubbed antennae, and only two wings – which was a clue that it had to be a fly of some sort. I took a little video with my cell phone and you can see it curling its abdomen under its body here…

After watching it a while longer, I took a few pictures and then did a little research to discover that this is a species of Mydas fly known as Mydas clavatus. Mydas flies are a family of the largest flies in North America, and this one was impressive at about one and 1/2 inches long. It’s name refers to King Mydas of Golden fame, perhaps because it has a distinct gold/orange band around the second segment of its abdomen.

Can you see the orange band on this Mydas fly’s abdomen and its clubbed antennae?

Mydas clavatus flies live in the eastern US in grasslands and woodlands. The adults lay single eggs in the soil or on or near rotting logs. The larvae prey on other grubs in the rotting logs or soil, especially the grubs of beetles that can be harmful to the roots of plants. Adults Mydas flies feed on mostly nectar and pollen and are especially attracted to the flowers of bee balm, butterflyweed and other Asclepias species, mountain mint and rattlesnake master. Our newly planted bee balm and milkweeds are blooming now, so perhaps these plants drew this impressive fly to our yarden.

Mydas clavatus – a Mydas fly that mimcs a spider wasp

The coolest thing about this Mydas fly, though, is that it is known as what’s called a Batesian mimic – a harmless species that gains protection from predators by mimicking a stinging, biting, or distasteful/toxic species. This Mydas clavata looks and acts a lot like a spider wasp, with its shiny, black/purple wings and curling abdomen.

The Mydas fly on our sheet mulch curls its abdomen under, mimicking a wasp stinging its prey.

Spider wasps, when grabbed by a young fledgling flycatcher bird, like our Eastern phoebes, sting the young bird and therefore teaches it not to eat it again! The Mydas flies happen to emerge as adults later in the summer than the spider wasps, so by the time they are flying about and potential prey for the flycatchers, the birds have already learned their painful lesson from the spider wasps and will leave the Mydas flies alone. How clever is that?!

Here’s a great lesson in timing – one that I will take to heart as I establish my pollinator and beneficial insect gardens BEFORE I plant my vegetable gardens next year!

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