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Marsh Fritillaries - Jewels of the Wet

By Taylor Wildlife, Jul 30 2019 02:00PM

Perhaps one of my favourite butterflies of the year, marsh fritillaries (Euphydryas aurinia) are the orange stained glass windows hiding in the bog and grassland. Their diverse pattern of orange, yellow and black make them fairly easily distinguished from the rest of the common fritillary family member in the Scotland and, in my opinion, much prettier (can you tell i'm biased?).

They are generally restricted to the western side of the UK, with many colonies on the west coast of Scotland. They are a UK Biodiversity Action Plan priority species due to their declining numbers across Europe as well as Britain. They were a welcome surprise on Mull one sunny day, spotted at the very beginning of the morning's survey, just a casual 10m away from a main road. Even if nothing else of note is seen on a survey, a day that includes a marsh fritillary is always one for the books.

Although the adults can be seen in May/June, the caterpillars become obvious in late summer/autumn as they hatch and congregate together to feed on their sole food source, devil's bit scabious (Succisa pratensis), a purple flowering plant. Talk about fussy eaters! Coincidentally, these plants also serve as dinner for the narrow-bordered bee hawk-moth (a mouthful in itself!), another worthy sighting for the record books. The marsh fritillary caterpillars spin larval webs that can house many individuals at once, making it an ideal time to conduct counts to provide population estimates. Although it is definitely less fun looking for black caterpillars in webs than it is chasing the adults through tussocky wet grassland on a sunny day! The caterpillars will utilise these tussocks to provide protection during the winter months as they hibernate and wait for the warmer weather to arrive.

Due to their locality in wet areas, the caterpillars are somewhat resistant to short term flooding but often suffer during bad winters, meaning populations can be very variable from year to year. With the overall declining population, any sightings of these beautiful butterflies are noteworthy and worth sending in to recording groups such as Butterfly Conservation. Here at Taylor Wildlife, we make sure to collate all our butterfly sightings over the survey season to send in to nationwide databases, contributing to the mapping and monitoring of rare species such as the marsh fritillary.

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