Bug FAQLarge Milkweed Bug
Oncopeltus fasciatus · Order: Hemiptera · Family: Lygaeidae
Also called: Milkweed bug
The large milkweed bug is a small (11-12 mm) hemimetabolous insect that lives in disturbed areas and open pastures across North America, from Central America up to southern Canada. It feeds mainly on milkweed seeds but will also eat aphids and monarch butterfly eggs or larvae when available. Development takes about a month, passing through four nymphal stages before becoming an adult; reproduction is year-round in the tropics and limited to warm months farther north.
Source: Wikipedia
Size
Adults measure about 11 to 12 mm in length.
Source: Wikipedia
Where it lives
They are found in disturbed sites such as roadsides and open pastures.
Source: Wikipedia
What it eats
They specialize on milkweed seeds but will opportunistically eat aphids and monarch butterfly eggs or larvae.
Source: Wikipedia
Life cycle
They undergo incomplete metamorphosis, developing through four nymphal instars over 28 to 30 days before molting into adults.
Source: Wikipedia
When you see it
In tropical areas they reproduce year-round; in temperate zones they breed during the warmer months. Southern populations often feed on the tropical milkweed Asclepias curassavica.
Source: Wikipedia
Where it comes from
Their range covers North America from southern Canada through the United States and Mexico to Central America, reaching as far south as Costa Rica.
Source: Wikipedia
Lookalikes
They are part of a Müllerian mimicry complex and are unpalatable to predators.
Source: Wikipedia
Where it is found in the US
Recorded in 47 of 51 states and DC. Most records: Texas, California, Illinois, Virginia, Ohio, New York, Maryland, Pennsylvania.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: native in North America; native in Canada; native in United States. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Same family (Lygaeidae)
Small Milkweed BugLygaeus kalmii
False Milkweed BugLygaeus turcicus
Indian Milkweed BugSpilostethus pandurusDamages trees, gardens or crops
Black-and-Red BugLygaeus equestris
Harlequin bugSpilostethus saxatilisDamages trees, gardens or crops
Darth Maul BugSpilostethus hospesDamages trees, gardens or cropsSources
- Wikipedia: https://en.wikipedia.org/wiki/Large_milkweed_bug
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-22 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-22.