Craesus septentrionalis
In 3 days ~10% in a week ~30%
Craesus septentrionalis, the flat-legged tenthred or birch sawfly, is a species of insect in the order Hymenoptera, the suborder Symphyta and the family Tenthredinidae. It was first described by Carl Linnaeus in 1758. The adult sawflies are black and brown with transparent wings and the larvae are yellowish-green and resemble caterpillars. The larvae feed on the leaves of various species of deciduous tree. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Bavarian Forest National Park | 🇩🇪 Germany | |
| 2 | Wadden Sea National Park | 🇩🇪 Germany |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Birmingham | 🇬🇧 United Kingdom | |
| 2 | Helsinki | 🇫🇮 Finland | |
| 3 | Paris | 🇫🇷 France | |
| 4 | Saint Petersburg | 🇷🇺 Russia |
Rare
Under 5% of wildlife watchers report a Hazel Sawfly sighting in Wadden Sea National Park on a given day, based on 12 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 422nd most-seen of the 818 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
June and September
In those months about 10% of wildlife watchers report a Hazel Sawfly in Wadden Sea National Park on a given day, against under 5% in July–August and October–May, the lowest months.
Between 1 and 4 pm
Across all the parks we cover, that three-hour window holds the most Hazel Sawfly sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
2nd of 2
Of the 2 parks where we can rate Hazel Sawfly sightings, Wadden Sea National Park ranks 2nd at under 5%. The best odds are in Bavarian Forest National Park (Germany, about 10%).
GBIF citizen-science records
It is estimated from how often the Hazel Sawfly is recorded against all the insects logged in Wadden Sea National Park (12 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.
