Here’s a detailed natural history overview of the Black-spotted Longhorn Beetle (Rhagium mordax), a striking longhorn species often found in European woodlands:

**Black-spotted Longhorn Beetle (Rhagium mordax)**

Taxonomy & Classification

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Cerambycidae (Longhorn beetles)
Subfamily: Lepturinae
Genus: Rhagium
Species: R. mordax

General Description

Size: 10–22 mm in length.
Body: Elongated and robust.
Coloration:
- Elytra (wing covers) are brownish or grayish with four irregular black spots on each.
- Pronotum is rough and marked, sometimes with darker patterns.
- Antennae relatively long but shorter than body length.
Distinctive features: The spotted elytra pattern makes it easy to distinguish from similar Rhagium species, such as Rhagium inquisitor.

Behavior & Lifestyle

Activity period: Adults are active in late spring to midsummer (May–July).
Diurnal: Seen on logs, tree trunks, and flowers during the day.
Flight: Capable of strong flight; often encountered in forest clearings.

Diet

Adults: Feed on nectar, pollen, and sometimes tree sap.
Larvae: Wood-borers that develop in decaying or recently dead coniferous trees, especially spruce and pine.

Life Cycle

Eggs: Laid in crevices of bark or in decaying wood.
Larvae: Bore into the wood, creating wide tunnels as they feed on the inner layers.
Development time: Usually 2–3 years in colder regions.
Pupation: Occurs inside the wood, followed by emergence of the adult beetle in spring.

Habitat

Mixed and coniferous forests.
Commonly associated with pine, spruce, and fir, though occasionally found in deciduous wood.
Adults often seen basking on tree trunks, logs, and fallen timber.

Geographic Range

Widespread across Europe and parts of western Asia.
Particularly abundant in boreal and temperate forests.

Ecological Role

Decomposer: Larvae contribute to the breakdown of dead wood, recycling nutrients into the ecosystem.
Pollinator: Adults visiting flowers may assist in pollination.
Prey species: Birds, parasitic wasps, and small mammals feed on both larvae and adults.

Similar Species

Rhagium inquisitor (Lesser-spotted longhorn): Smaller, with finer markings.
Rhagium bifasciatum (Two-banded longhorn): Has yellowish cross-bands instead of irregular black spots.

Conservation Status

IUCN Red List: Not globally assessed; considered locally common and widespread.
Threats:
- Loss of old-growth and decaying wood habitats due to forestry practices.
- Removal of fallen logs and deadwood from forests.
Conservation importance: Protecting deadwood habitats supports this and many other saproxylic (wood-dependent) insects.

Interesting Facts

One of the first longhorn beetles to appear in spring, often spotted on sunny days in May.
Larval tunnels of R. mordax can help other insects and fungi colonize dead wood.
Despite being a longhorn beetle, its antennae are not as exaggeratedly long as in many tropical relatives.