47696_male_Haute-Savoie_25Jul20

A Boloria species with a very limited distribution in France, its main region being northern Europe and Fennoscandia. This distribution just spills across the border into north-eastern France, with additional isolated regions, mainly in the Massif Central. It is essentially a wetland species of elevated peat bogs where its larval hostplant, Vaccinium oxycoccos (UK name: Cranberry - hence the English name) grows. It is usually found in the vicinity of light woodland and near open water.

It is a species that occurs from lowland to higher altitudes, but generally not at the high altitudes of its Boloria cousins such as Mountain Fritillary (B. napaea), Shepherd's Fritillary (B. pales) or Balkan Fritillary (B. graeca). Its habitat requirements means that it is unlikely to be confused with any other Boloria species except Titania's Fritillary (B. titania). An identification clue, should it be needed, is that the upf mark in discal s1 is particularly v-shaped.

According to T&L, males, despite their bright colouring, have an ability to disappear in flight. This was certainly my experience with the one aquilonaris I saw in 2020.

Its flight period is said to be from mid-June to August, but it appears that the flight period at any specific location is much shorter. Its limited distribution and flight period mean that it almost certainly requires a specific visit to a known location at the right time. As such, it is a species that I only saw for the first time in 2020 - many thanks to Philippe D for the location information.

However, a visit to a known but remote site in Loire on 18 July 2021 with the local experts proved to be too early as aquilonaris had not yet emerged. A return visit scheduled for 16 July 2023 looked to be too early as 2023 was shaping up to be a "late" year, but local knowledge - thank you Claude - said that it was out earlier than expected and indeed on 16 July, as is evident from these images, the males were showing signs of wear as were some females.

At this location, the entire population of maybe twenty individuals was restricted to a remote damp region where Marsh Cinquefoil (Potentilla palustris) grew, as can be seen from these 2023 images.

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having arrived at the specified location at 07.45 to find cloud cover and nothing flying, I waited for some four hours for the clouds to part just a little and the effect was astonishing as the whole area came to life. After several false alarms which turned out to be either titania or Lesser Marbled Fritillaries (Brenthis ino), a medium-sized fritillary came into view which was clearly neither of these. Having learnt from past mistakes, I remembered to get a photograph, even from distance, if only for confirmation, and then to get closer for a better photograph. The result is the image 47696 below. However, the opportunity for a better photograph never arrived. It had disappeared completely and another two hours of waiting and scouring the landscape with my trusty Papilio binoculars revealed nothing. T&L was right. But a life tick (I don't have many left to go) isn't to be sniffed at. I strongly suspect that this male, which appeared pristine, was the first to emerge and that 2020 was a "late" year.

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