humpbacked phorid flies

Humpbacked fly (Megaselia scalaris). Photo: Whitney Cranshaw, Colorado State University,

Updated: March 1, 2023

About phorid flies

  • Their common name, humpbacked fly, reflects their humpbacked appearance. 

  • Adults are about 1/64 - 1/4" in size. 

  • There are several species of small black flies that may occasionally become pests in buildings.

  • These can include phorid flies which breed in decaying organic matter of plant or animal origin. 

  • Extremely large numbers of phorid flies on the first floor of a structure may indicate a broken drain or sewer line under the structure.

  • Removing or drying the organic matter where the larvae live will eliminate the problem.