Bug FAQRain Beetle
Pterostichus melanarius · Order: Coleoptera · Family: Carabidae
Also called: European dark harp ground beetle
Adult rain beetles are 12 to 18 mm long and black with straight lines on their wing covers. They live in wet places across a wide temperature range and can be found in forests, meadows, cities and farms. Native to Europe, they have spread to North America since the 1920s and hunt other small invertebrates.
Source: Wikipedia
How to recognize it
They are black with straight striations on the elytra and have a laterobasal carina and denticulate posterior angles on the pronotum, which set them apart from other Pterostichus species.
Source: Wikipedia
Size
Adults measure between 12 and 18 mm in length.
Source: Wikipedia
Where it lives
The species prefers moist environments and tolerates a broad range of temperatures. It can live in forests, meadows, urban settings and cultivated land.
Source: Wikipedia
What it eats
It is a predator that feeds on other invertebrates. It may also ingest insecticides indirectly by eating contaminated prey.
Source: Wikipedia
Life cycle
Mating takes place in early fall, followed quickly by egg laying.
Source: Wikipedia
When you see it
Reproduction occurs in the early autumn months.
Source: Wikipedia
Where it comes from
Originally European, it has been introduced to North America since the 1920s.
Source: Wikipedia
Lookalikes
They are distinguished from other Pterostichus beetles by the laterobasal carina and denticulate posterior pronotum angles.
Source: Wikipedia
Where it is found in the US
Recorded in 35 of 51 states and DC. Most records: Wisconsin, Michigan, North Dakota, Washington, Vermont, Utah, Pennsylvania, Oregon.
Darker = more records. Counts are museum and citizen-science records, not population size.
Source: GBIF
Status: introduced in North America; introduced in Canada; introduced in United States. Source: iNaturalist
Months it is reported in the US
Source: GBIF
More photos
Same family (Carabidae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Pterostichus_melanarius
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.