Oct 24, 2012 – What Kind of Little Fly?


We have a customer that recently had the black worms coming up in his commode identified as "black scavenger fly larvae" or Sepsidae larvae. We are unfamiliar with this fly species. Would this infestation be treated like a drain fly infestation?


Well, Sepsids are more associated with feces and decaying plant materials than the wet organic sludge of the drain fly larvae, but it is possible that either could breed in the same unsanitary setting. And, since this is a commode it certainly could provide the proper breeding conditions for the larvae of Sepsids. I'm not certain myself that I would recognize the larvae of black scavenger flies, but those of drain flies are fairly distinctive in appearance. 

But, yes, you would treat either kind of fly in the same manner with respect to eliminating the materials that the larvae are using to feed in. Since so many of the small flies found inside structures are indicators of unsanitary or some other unwanted condition (excessive moisture, fungus, accumulations of wet organic sludge) it is important and appropriate to clean up that setting to eliminate the larvae as well as to create a more healthful environment for people. Now, exactly what you mean by "coming up" in his commode I am not certain, but if you are suggesting that these larvae are actually coming up from the water at the bottom of the toilet.............well, yuck! Is it an equally yucky possibility that somewhere above waterline in this toilet there is some hidden accumulation of, well, "splatter" that has been ignored?

For drain flies living in the sludge within a sink or floor drain the resolution may be more clear cut for us, using one of the many drain cleaners to eat away that sludge and in the process eliminate the fly larvae as they lose their food resource. For a toilet it still is going to be a cleaning process but you may need to identify just where the cleaning needs to be. 

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