Adults are only about 4–7 mm long.
Fine-art photographic collection
Poecilium alni
A longhorn beetle small enough to develop inside twigs, using branches too thin for most of its relatives.
About this species
Poecilium alni(Linnaeus, 1767)
Information reviewed15 July 2026
Poecilium alni is a tiny Eurasian longhorn beetle associated with recently dead or weakened branches of broad-leaved trees. Adults are dark with contrasting pale marks and are most often seen in spring.
Taxonomy
Animalia · Arthropoda · Insecta · Coleoptera · Cerambycidae · Poecilium
Accepted taxon. · checked 2026-07-15
Europe to western AsiaBroad range and selected reference localities — not a complete occurrence map.
Europe to western Asia
Woodland edges, old orchards and broad-leaved forest with fine dead branches.
Adults are active mainly from April to June.
Larvae tunnel in thin dead branches; adults take plant fluids and may visit blossom.
Solitary.
What makes this species remarkable?
At only a few millimetres long, the entire larval development can take place inside a twig little thicker than a pencil, exploiting wood that larger longhorns cannot use.
Rearing records span oak, sweet chestnut, alder, maple, elm and hazel, but the larvae target a very specific condition: weakened or freshly dead small branches rather than sound timber.
The hidden adult can be detected with synthetic pheromone blends, allowing researchers to survey an insect that spends most of its life sealed inside wood without cutting open its habitat.