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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

A fly with a golden touch? Mydas fly, Mydas clavatus


Mydas flies are among the largest of all flies in the world.


One of my favorite mythological tales is that of King Midas, the ruler of Phrygia who wished for and was granted the power to turn everything he touched into gold. Apparently, this was his undoing as he starved to death when the food he touched turned into inedible gold - poor guy. While watching some busy bumble bees pollinating butterfly weed, I had a golden opportunity to witness an unusual two-winged visitor, the spectacular Mydas fly. Mydas clavatus is a member of a relatively small family of very large flies whose biology remains largely unknown.

Stealthy black wings of the mydas fly give it a waspish appearance.

Mydas clavatus is among the largest of all North American flies, with a body length often more than an inch. It is believed that their black–velvet coloration presents the visage of a large stinging wasp. This confers protection from enlightened predators that have learned not to mess with painful black stinging insects. One report holds that they also have a behavioral mimicry in which they curl their abdomen and jab in a mock stinging routine aimed to fool potential predators.

Adult flies have been observed dining on the nectar and pollen of flowers of Spiraea alba, Pycnanthemum virginianum, Asclepias syriaca, A. verticillata, Monarda punctata, Teucrium canadense, Verbena hastata and Saponana officinali. Perhaps the abundance of butterfly weed in my flower bed served as a beacon for this unusual visitor. Female mydas flies deposit eggs in soil and rotting wood where their predaceous larvae dine on other soft bodied insects, including the grubs of scarab beetles, kin of the ones we met in last week’s episode “Blossom busters – Oriental beetle, Anomala orientalis.

The adult mydas fly that visited my garden was rather tranquil and allowed several photographs before flying away for some unknown fly business. Unfortunately for me, the mydas fly lacked the Midas touch and the holly and pumpkin on which it perched failed to turn to gold. Still, seeing one of these unusual creatures provided a golden moment for a bug geek.



Time to groom a bit.


Bug of the Week thanks Dr. Shrewsbury for capturing the image of the mydas fly and providing the inspiration for this episode. The delightful account “Adult female Mydas clavatus (Diptera: Mydidae) feeding on flowers in Wisconsin” by Andrew H. Williams and the interesting web page “Mydas fly” by Jeffrey K. Barnes were used as references. To learn more about this cool large fly, please visit the following link: