Phytomyza ilicis
In 3 days ~40% in a week ~70%
Phytomyza ilicis, the holly leaf miner, is a leaf mining fly in the family Agromyzidae, whose larvae burrow into leaves of the holly tree (Ilex aquifolium) leaving characteristic pale trails or leaf mines. Adults of P. ilicis are small with a wing length measuring 2.5–3 millimetres (0.098–0.118 in). They have red eyes and 6–8 pairs of acrostichal bristles on the thorax.
Larvae are pale, leg-less maggots lacking a head capsule and thoracic and abdominal legs like most fly larvae. The dark-brown coloured puparium is formed from the hardened last larval skin. The holly leaf miner is found throughout the holarctic on its host Ilex aquifolium. It is common and widespread in Europe and has been introduced into western Canada and north west USA. Its distribution is probably dependent upon average temperatures; Peterkin and Lloyd found it absent from areas where the mean temperatures of the coldest months of the year falls below −0.5 °C (31.1 °F).
Female Agromyzidae insert an egg in the leaf tissue using an ovipositor. In the case of P. ilicis this poses a problem, because the leaf of the hostplant is unusually tough. Only during the annual... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Snowdonia National Park | 🇬🇧 United Kingdom | |
| 2 | Wadden Sea National Park | 🇩🇪 Germany | |
| 3 | Great Bear Rainforest | 🇨🇦 Canada |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Liverpool | 🇬🇧 United Kingdom | |
| 2 | Birmingham | 🇬🇧 United Kingdom | |
| 3 | London | 🇬🇧 United Kingdom | |
| 4 | Manchester | 🇬🇧 United Kingdom | |
| 5 | Vancouver | 🇨🇦 Canada | |
| 6 | Berlin | 🇩🇪 Germany | |
| 7 | Brussels | 🇧🇪 Belgium | |
| 8 | Leeds | 🇬🇧 United Kingdom | |
| 9 | Dublin | 🇮🇪 Ireland | |
| 10 | Rotterdam [The Hague] | 🇳🇱 Netherlands |
With luck
About 10% of wildlife watchers report a European Holly Leafminer sighting in Snowdonia National Park on a given day, based on 30 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 92nd most-seen of the 387 insects we can rate there. Over three days the chance rises to about 40%, and over a week to about 70%, if each day is a fresh chance.
March and November
In those months about 40% of wildlife watchers report a European Holly Leafminer in Snowdonia National Park on a given day, against under 5% in February and June, the lowest months.
Between 1 and 4 pm
Across all the parks we cover, that three-hour window holds the most European Holly Leafminer sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Yes
Of the 3 parks where we can rate European Holly Leafminer sightings, Snowdonia National Park has the highest daily chance: about 10%. Next come Wadden Sea National Park (Germany, about 10%) and Great Bear Rainforest (Canada, under 5%).
Same order: Diptera
The closest relatives of the European Holly Leafminer that you can see in Snowdonia National Park (order Diptera, Flies) are Tapered Drone Fly (about 20%), Marmalade Hover Fly (about 20%) and Dark Giant Horse Fly (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the European Holly Leafminer is recorded against all the insects logged in Snowdonia National Park (30 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.
