Bug FAQForest shield bug
Oncacontias vittatus · Order: Hemiptera · Family: Acanthosomatidae
The forest shield bug is a small yellow-green true bug with a brownish hardened wing and a red V marking on its back. It lives in leaf litter, moss, under logs and on sunny walls or fences in New Zealand, feeding on Coriaria arborea as an adult and on grasses as a juvenile.
Source: Wikipedia
How to recognize it
Its body is yellowish to greenish, with a creamy-yellow margin on the pronotum and greenish smooth legs. The forewings are brown with creamy edges and a translucent tip, and a red V shape appears across them. The head and thorax are yellowish to greenish, the antennae are uniformly brown, and the lower side of the head matches the upper coloration.
Source: Wikipedia
Size
Adult males measure about 8.7 to 10.4 mm, while females are slightly larger at 10.3 to 11.7 mm. Juveniles are roughly 7.1 to 7.4 mm long.
Source: Wikipedia
Where it lives
They are collected from leaf litter, moss, under logs and at plant bases. They are also seen basking in the sun on walls and fences in human-modified areas.
Source: Wikipedia
What it eats
Adults feed on the plant Coriaria arborea and probably other vegetation. Juveniles prefer to eat grasses.
Source: Wikipedia
Life cycle
The bug goes through five instars before reaching adulthood. It produces one generation per year.
Source: Wikipedia
When you see it
Adults are most common in spring but can be found year-round. Mating occurs from late October to early November.
Source: Wikipedia
Where it comes from
This species is found only in New Zealand.
Source: Wikipedia
Lookalikes
The eggs are parasitised by the wasp Trissolcus maori.
Source: Wikipedia
More photos
Questions people ask
How big are forest shield bugs?
Males are about 8.7 to 10.4 mm long and females 10.3 to 11.7 mm; juveniles are around 7.1 to 7.4 mm.
Source: Wikipedia
What do forest shield bugs eat?
Adults feed on Coriaria arborea and likely other plants, while juveniles mainly eat grasses.
Source: Wikipedia
Where can I find forest shield bugs?
They live in leaf litter, moss, under logs, at plant bases, and also on sunny walls and fences.
Source: Wikipedia
When do forest shield bugs mate?
Mating takes place from late October to early November.
Source: Wikipedia
Same family (Acanthosomatidae)
Sources
- Wikipedia: https://en.wikipedia.org/wiki/Oncacontias
Look it up elsewhere: GBIF · iNaturalist · BugGuide · ITIS · Wikipedia
Text written 2026-10-23 from the sources above and checked sentence by sentence against them. Data fetched 2026-10-23.