Bugging You From San Juan Island

There is no way I can save this fly to post for Fantastic Fly Fridays, so I am improvising here and making a special DAY for a very cool fly. Marsh Fly Monday, it must be!

This is, as the title suggests, a Marsh Fly in the family Sciomyzidae (say “/sigh-oh-MIZ-ih-dee/”). The etymology of the name is from Greek skia meaning ‘shadow’ and myzo meaning ‘to suck.’ They are named so because the aquatic larvae of this group are parasitoids of snails, slugs, and fingernail clams. They are also referred to as Snail Killers. Some larvae are actually predatory and “hunt and kill” up to 30 snails before they reach their pupation stage of development. This particular species is Sepedon fuscipennis.

I observed this specimen for a few minutes in our unmowed yard. It’s got very cool, grasshopper-like hind legs, and weirdly, it moved (quite adeptly) backward when it was in the grass, before finally flying off.

If you are curious to know more, check out the reference section below. Always be curious!

Thanks for reading.

References

Bugguide. 2026. Sciomyzidae. Bugguide.net. Iowa State University. https://www.bugguide.net/node/view/7740

Bugguide. 2026. Sepedon fuscipennis. Bugguide.net. Iowa State University.

Cole. F. 1969. The Flies of Western North America. University of California Press Berkeley and Los Angeles.

ELBERG, KAUPO & ROZKOŠNÝ, RUDOLF & Knutson, Lloyd. (2009). A review of of the Holarctic Sepedon fuscipennis and S. spinipes groups with description of a new species (Diptera: Sciomyzidae). Zootaxa. 2288. 51-60. 10.11646/zootaxa.2288.1.3.

Peterson, M. 2018. Pacific Northwest Insects. Seattle Audubon Society.