Japanese assassin bug
First recorded in Japan in the 1930s after arriving from China, this assassin bug ambushes prey on tree trunks and bites painfully if handled.
| Where | Tree trunks in parks across East Asia |
|---|---|
| Size | 16 to 24 mm body length |
| When | March to June and August to November |
The Japanese assassin bug is a large, glossy black assassin bug 16 to 24 millimetres long. White plates edged with black spots run along the sides of the abdomen, and newly molted individuals are briefly bright red before darkening.
Nymphs gather in groups on the trunks of cherry, zelkova, mulberry, and other large trees in parks and along roadsides, where they ambush and pierce other insects. Originally from China and continental Southeast Asia, it has spread through Japan since the 1930s, overwintering as a larva and emerging as an adult the following spring.
Traits
Habitat
Towns
Colour
Black, White
Active
Day
To people
Take care
Its piercing bite causes intense, lasting pain, so it should never be handled bare-handed, though it does not seek out people on its own.
Activity through the year
Often confused with
More slender bodied and usually found on leaves and grass rather than on the tree trunks where the bulkier Japanese assassin bug gathers.
Questions
Is the Japanese assassin bug dangerous to people?
Take care. Its piercing bite causes intense, lasting pain, so it should never be handled bare-handed, though it does not seek out people on its own.
When can you see the Japanese assassin bug?
The Japanese assassin bug can be seen from March to June and August to November, by day.
Plate retouched from a photo by plant 0302, CC BY 4.0, iNaturalist Licence
Report a mistake in this entry
True bugs›Assassin bugs›Agriosphodrus
Last updated 2026-09-27. Every entry is checked against published sources.