Bug FAQStout Spanworm Moth
Lycia ursaria · Order: Lepidoptera · Family: Geometridae
Also called: Stout Spanworm
Source: Wikipedia
Adults have a wingspan of about 45 mm. They are active from March through June, producing one generation each year. The caterpillars eat leaves of a wide range of broad-leaved trees and shrubs, which can harm those plants.
Source: Wikipedia
How to recognize it
Lycia ursaria, known as the stout spanworm moth or bear, belongs to the Geometridae family.
Source: Wikipedia
Size
The moth’s wingspan measures roughly 45 mm.
Source: Wikipedia
What it eats
Larvae feed on leaves of many broad-leaved trees and shrubs such as alders, apples, ashes, lindens, birches, blueberries, dogwoods, elms, hawthorns, poplars and willows.
Source: Wikipedia
Life cycle
Adults are on the wing from March to June, with one generation per year.
Source: Wikipedia
When you see it
The flight period for adults runs from early spring through early summer.
Source: Wikipedia
Where it comes from
Its native range includes southern Canada and the northern United States, down to New Jersey and Iowa.
Source: Wikipedia
Where it is found in the US
Recorded in 25 of 51 states and DC. Most records: Michigan, Pennsylvania, New York, Minnesota, Connecticut, Illinois, Wisconsin, Massachusetts.
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 trees do the larvae eat?
The caterpillars consume leaves of alders, apples, ashes, lindens, birches, blueberries, dogwoods, elms, hawthorns, poplars and willows.
Source: Wikipedia
When are adult stout spanworm moths active?
Adults fly from March through June, producing a single generation each year.
Source: Wikipedia
Same family (Geometridae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Lycia_ursaria
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-24 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-24.