Yep, so came back from vacation (a sewer pipe had bust the day we left) to an all out infestation of [drain flies](ww.google.ca/imgres?imgurl=https%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fthumb%2Ff%2Ff5%2FClogmia_Albipunctata_or_moth_fly.jpg%2F1200px-Clogmia_Albipunctata_or_moth_fly.jpg&imgrefurl=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FDrain_fly&docid=_QzXg1WkSsM06M&tbnid=dOab7qGLiEHHwM%3A&vet=10ahUKEwi1vuO4--DVAhWIOSYKHYunDsQQMwhhKAIwAg..i&w=1200&h=960&bih=505&biw=1047&q=drain flies&ved=0ahUKEwi1vuO4--DVAhWIOSYKHYunDsQQMwhhKAIwAg&iact=mrc&uact=8)
Dozens of hours of vacuuming later (filled 2 bags with these little fuckers) and a very costly plumber visit, it turns out tree roots have poked through the outgoing sewer pipe and blocked it.
The pipe had been leaking for a while, filling a depression in the ground under the basement floor and soaking the ground in the process.
Résultat des courses; We need to blast the roots out of the pipe, fix it, so it doesn't leak and the kicker, wait for it....remove the entire basement floor to clean out the mucky water and let the ground dry up.
....sigh...