Entity scope
This profile centers on the North American boxelder bug, Boisea trivittata. Similar true bugs require pattern, anatomy, host, season, and geography together.
Quick identity
- Scientific name
- Boisea trivittata
- Entity scope
- One North American true-bug species
- Adult
- Elongate black body with narrow orange-red lines and overlapping wings
- Nymph
- Bright red when young, becoming red and black as it develops
- Useful context
- Boxelder or related host trees, sunny surfaces, and fall aggregation near buildings
- Key limit
- Red and black coloration alone is not species proof
Key characteristics
- Adults are elongated true bugs, commonly around 12 mm long, with black wings and narrow reddish-orange edging and lines.
- The folded forewings overlap to produce an X-like true-bug outline.
- Young nymphs are much redder than adults and gain darker wing pads and markings as they develop.
- Pattern, body proportions, host context, season, and geography are more reliable together than one color feature.
Life stages
01
Nymph
Initially bright red and wingless, later red and black with developing wing pads.
02
Adult
Black-and-red winged stage that can aggregate and enter protected building spaces for winter.
Where it is found
- On and near seed-bearing boxelder trees and sometimes related maples or ash.
- Warm sunny exterior walls and sheltered cracks during late-summer and fall aggregation.
- Around windows and indoor living spaces after overwintering adults become active; they do not normally reproduce indoors.
Behavior and activity
- Adults may fly from host areas to warm exposed buildings before winter.
- Overwintering adults can become active on mild sunny days and move toward indoor light.
- Large seasonal aggregations do not automatically mean feeding or reproduction is occurring inside.
Diet and resources
- Seeds and plant material associated especially with boxelder trees.
- Plant feeding is different from structural feeding; building entry is primarily for shelter.
Associated signs
Repeated black-and-red adults on sunny building surfaces supports seasonal shelter-seeking, not structural damage or indoor breeding.
Common lookalikes
Broader shield-shaped true bugs with different body proportions and markings.
Several true bugs share red-and-black patterning and need closer anatomy and regional context.
Red-and-black seed bugs with different markings, host plants, and body proportions.
Why it matters
A seasonal nuisance without exaggerated damage claims
Boxelder bugs can enter buildings in large numbers and may stain surfaces when crushed, but they normally do not reproduce indoors or cause serious structural damage.
- Aggregation size varies by season and site.
- One indoor adult does not establish an infestation or a damaged host tree.
Management direction
- Confirm the adult or nymph pattern and record season and nearby host context.
- Separate outdoor aggregation from insects already sheltered inside.
- Use high-level physical removal and entry-reduction guidance rather than treating the Profile as a pesticide program.
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Identify a photoReviewed guidance and sources
Last reviewed August 2026. Sources support the claims listed with them; their limits remain part of the review.
- ITIS — Boisea trivittata
Supports: Accepted species identity and taxonomic placement of Boisea trivittata.
Does not support: Behavior, building entry, risk, or identity from one photograph.
Scope note: Taxonomic reference only.
- University of Minnesota Extension — Boxelder bugs
Supports: Adult and nymph appearance, host context, seasonal aggregation, overwintering entry, and nuisance-level significance.
Does not support: Identity from color alone or a universal seasonal pattern outside the stated region.
Scope note: North American household and landscape context; species, range, season, and local conditions vary.