A collaboration of coast and countryside organisations on The Lizard Peninsula

Catkins may have appeared on the willow and the blackthorn may be flowering but the sign of spring I look forward to most is spotting the bristly little black caterpillars of the marsh fritillary butterfly basking together on freshly spun webs!

Marsh fritillary caterpillars

Marsh fritillary caterpillars

These caterpillars have spent the winter huddled together in a spun ‘nest’ deep down in the vegetation and, during the first warm days of spring, they reappear to spin a new communal web on the leaves of devil’s-bit scabious (Succisa pratensis) - the food plant of the caterpillar. They construct a communal web and cluster together to form a black ‘mass’ which can more efficiently absorb the sun’s warmth and raise their body temperatures in order to seek out and digest food. I have also found larval webs constructed on the stems of grasses, but scabious is never far away, with caterpillars basking on both leaves, grass and mosses.


Marsh fritillary caterpillarsMarsh fritillary caterpillars

These larval webs are fairly easy to spot but you have to be quick as soon the caterpillars, having feasted and moulted, start to move away from the group and live singly. They can still be found if you focus on looking for their food plant, devil’s-bit scabious, which can soon get munched away to just the main stem!

Marsh fritillary butterfly

Marsh fritillary butterfly

Devils bit ScabiousMarsh fritillaries have been recorded on 16 sites (and their associated sub-sites) on The Lizard over the past couple of years. If you miss seeing the caterpillars keep your eyes open from the end of May into June on sites with devil’s-bit scabious, commonly within damp grasslands with clumps of purple moor-grass (Molinia caerulea), although they are also present on Predannack and Mullion Cliffs with their patches of scabious.

 

 Devils bit Scabious

Published:  April 2019
Author: Sarah Board (Biodiversity Projects Officer (voluntary))