Rhagium mordax
In 3 days ~20% in a week ~50%
Rhagium mordax, the black-spotted longhorn beetle, is a species of long-horned beetle. This beetle is found throughout Europe and to Kazakhstan and Russia. Larvae develop in silver fir, hazel, European weeping birch, European beech, and the European chestnut. Ischnoceros rusticus is an ichneumonid parasitoid wasp that feds on Rhagium mordax larvae.
Rhagium mordax grows from 13 to 26 millimetres (0.51 to 1.02 in) long. In colour, they are mixed ochre and black, with one black splotch on each elytron accompanied by two pale lines on either side. The beetles' bodies are covered with small yellow hairs, although one distinguishing feature of the species is two bald spots on its elytra.
Rhagium mordax has a long, narrow head with a distinct neck. The insect's face bears a suture and the temples are elongate with some stiff hairs. The antennae are relatively short and the first segment is wider at its tip and longer.
Rhagium mordax was first named Leptura mordax by Charles De Geer in 1775. There are five formally described varieties: Rhagium mordax var. altajense Plavilstshikov, 1915 Rhagium mordax var. klenkai Heyrovský, 1914 Rhagium mordax... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Triglav National Park | 🇸🇮 Slovenia | |
| 2 | Białowieża National Park | 🇵🇱 Poland | |
| 3 | Cairngorms National Park | 🇬🇧 United Kingdom | |
| 4 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 5 | Bavarian Forest National Park | 🇩🇪 Germany |
With luck
About 10% of wildlife watchers report a Blackspotted Longhorn Beetle sighting in Snowdonia National Park on a given day, based on 9 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 227th most-seen of the 387 insects we can rate there. Over three days the chance rises to about 20%, and over a week to about 50%, if each day is a fresh chance.
May
In that month about 20% of wildlife watchers report a Blackspotted Longhorn Beetle in Snowdonia National Park on a given day, against under 5% in July to March, the lowest months.
Between 1 and 4 pm
Across all the parks we cover, that three-hour window holds the most Blackspotted Longhorn Beetle sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
4th of 5
Of the 5 parks where we can rate Blackspotted Longhorn Beetle sightings, Snowdonia National Park ranks 4th at about 10%. The best odds are in Triglav National Park (Slovenia, about 20%), Białowieża National Park (Poland, about 10%) and Cairngorms National Park (United Kingdom, about 10%).
GBIF citizen-science records
It is estimated from how often the Blackspotted Longhorn Beetle is recorded against all the insects logged in Snowdonia National Park (9 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
