Bug FAQRusty Dot Pearl
Udea ferrugalis · Order: Lepidoptera · Family: Crambidae
Also called: Rusty Dot
Source: Wikipedia
Adult rusty dot pearls have a wingspan of about 18 to 22 mm, while their caterpillars grow to 10 to 15 mm long. The larvae feed on many herbaceous plants such as mint, strawberry and ragwort, and can become a pest of crops.
Source: Wikipedia
How to recognize it
The forewings are yellow, brown or rust-colored with vague dark markings near the edges, and the hindwings are brownish-grey; the legs appear whitish.
Source: Wikipedia
Size
Adults have a wingspan of 18 to 22 mm. Caterpillars reach 10 to 15 mm in length.
Source: Wikipedia
Is it a pest in the house?
The species is sometimes regarded as a pest because its larvae attack various crop plants.
Source: Wikipedia
Where it lives
They spend the winter in the soil as a chrysalis.
Source: Wikipedia
What it eats
Larvae feed on herbaceous plants such as Stachys, Arctium, Lycopus, mint, Eupatorium cannabinum and wild strawberry.
Source: Wikipedia
Life cycle
The moth can have two or three generations per year. It overwinters in the soil as a chrysalis.
Source: Wikipedia
When you see it
Adults are on the wing throughout the year but are most common in autumn, depending on location.
Source: Wikipedia
Where it is found in the US
Recorded in 1 of 51 states and DC. Most records: Pennsylvania.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Months it is reported in the US
Source: GBIF
More photos
Questions people ask
What plants can the rusty dot pearl damage?
Its larvae feed on herbaceous plants such as mint, wild strawberry and ragwort, and can become a crop pest.
Source: Wikipedia
When are these moths active?
Adults fly throughout the year but are most frequently seen in autumn.
Source: Wikipedia
How large are the adults and caterpillars?
Adults have a wingspan of 18 to 22 mm, while caterpillars grow to 10 to 15 mm long.
Source: Wikipedia
Same family (Crambidae)
Box Tree MothCydalima perspectalisDamages trees, gardens or crops
Celery Leaftier MothUdea rubigalisDamages trees, gardens or crops
Elegant Grass-veneerMicrocrambus elegans
Hawaiian Beet Webworm MothSpoladea recurvalisDamages trees, gardens or crops
Garden Grass-veneerChrysoteuchia culmellaDamages trees, gardens or crops
Bluegrass Webworm MothParapediasia teterrellusDamages trees, gardens or cropsSources
- Wikipedia: https://en.wikipedia.org/wiki/Udea_ferrugalis
Look it up elsewhere: GBIF · iNaturalist · BugGuide · Wikipedia
Text written 2026-10-22 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.