[Last Modified: ]

September 2009
Answer to Case 260

The images in this case showed an aquatic larva of a fly in the family, Psychodidae.  These organisms are not parasitic and an appropriate answer should have been No Parasites Found (NPF).  Larvae of Psychodidae and related flies develop in standing water, including toilets.  Their presence in a toilet may lead one to believe that the larvae were shed during urination or defecation.  As such, they are often sent to public health laboratories for identification.  It is important that a diagnostic microbiologist be able to distinguish these organisms from true parasites.  Morphologic features of free-living aquatic fly larvae include a defined head capsule, long, thin setae, gills, and breathing tubes (red arrow, Figure C).

C

To view more images of artifacts, please click here.