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 Saint Petersburg on a given day, based on 6 verified sightings from GBIF citizen-science data. It is the 332nd most-seen of the 448 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 Saint Petersburg on a given day, against under 5% in September to July, the lowest months. That is one of Saint Petersburg's wettest months, with about 100 mm of rain against 40 mm in February.
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, Saint Petersburg ranks 4th at under 5%, level with the leaders once rounded. The best odds are in Birmingham (United Kingdom, under 5%), Helsinki (Finland, under 5%) and Paris (France, under 5%).
GBIF citizen-science records
It is estimated from how often the Hazel Sawfly is recorded against all the insects logged in Saint Petersburg (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.
