Craesus septentrionalis
In 3 days ~10% in a week ~20%
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 Helsinki on a given day, based on 6 verified sightings from GBIF citizen-science data. It is the 665th most-seen of the 838 insects we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
August
In that month about 10% of wildlife watchers report a Hazel Sawfly in Helsinki on a given day, against under 5% in September to July, 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.
Among the best
Of the 4 cities where we can rate Hazel Sawfly sightings, Helsinki ranks 2nd at under 5%, level with the leaders once rounded. The best odds are in Birmingham (United Kingdom, under 5%).
Same family: Tenthredinidae
The closest relatives of the Hazel Sawfly that you can see in Helsinki (family Tenthredinidae, Common Sawflies) are Turnip Sawfly (about 10%), Willow Redgall Sawfly (about 10%) and Tenthredo campestris (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Hazel Sawfly is recorded against all the insects logged in Helsinki (6 verified sightings), 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.
