A dark-winged fungus gnat (Bradysia sp.)

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Diptera Taxonomy

Sciaridae - Wikipedia
Bradysia spp. - University of Florida
Genus Bradysia - BugGuide

On March 10, 2017, I finally managed to get some photos of the 2 mm fungus gnats that were invading the soil of my garden seedlings growing under grow lights in my house.

This is a male, with a vertical pincher at the end of his abdomen.
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 This is a female. Note the absence of a pincher at the end of the abdomen.
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The gnat is standing on the wider top section of a small seedling container. That section is a little less than half an inch tall.
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Between my use of a clip-on macro lens, and the gnats' continuous jerky movement, it was hard to keep the video in focus.