Bug FAQWaltzing Fly
Prochyliza xanthostoma · Order: Diptera · Family: Piophilidae
Source: Wikipedia
Adults are 4 to 6 mm long, with males having heads about 1.24 mm long and 0.84 mm wide. They are narrow, brown flies with orange legs on the inner side, black legs on the outer side, and a thin silver line below the eyes. Larvae develop on carcasses but also infest cheeses and cured meats, making them a pantry pest.
Source: Wikipedia
How to recognize it
Adults are narrow and brown with orange legs on the inner side and black legs on the outer side. A thin silver line runs beneath their eyes.
Source: Wikipedia
Size
Body length ranges from 4 to 6 mm. Male head length averages 1.24 mm and width 0.84 mm.
Source: Wikipedia
Is it a pest in the house?
Larvae are found in cheeses and cured meats, so they are considered a pantry pest.
Source: Wikipedia
Where it lives
They are found throughout North America, especially near carcasses where they lay eggs, during the warmer seasons.
Source: Wikipedia
What it eats
Larvae feed on animal carcasses and also on cheeses and cured meats.
Source: Wikipedia
Life cycle
The sex ratio is strongly biased toward females. Adult males must fight each other for mates in a polygynous system.
Source: Wikipedia
When you see it
Adults are active in spring, summer, and fall.
Source: Wikipedia
Where it comes from
The species occurs across North America.
Source: Wikipedia
Where it is found in the US
Recorded in 34 of 51 states and DC. Most records: Maryland, Indiana, Missouri, Texas, Virginia, Illinois, North Carolina, Ohio.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: native in North America; native in Canada. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
What do the larvae eat?
They develop on carcasses but also infest cheeses and cured meats.
Source: Wikipedia
How can I identify a waltzing fly?
Look for a narrow brown body, orange legs on the inner side, black legs on the outer side, and a thin silver line under the eyes.
Source: Wikipedia
Are they a problem in my pantry?
Yes, their larvae can infest stored cheeses and cured meats.
Source: Wikipedia
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Prochyliza_xanthostoma
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-27 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-27.