Celastrina argiolus
Refresh page if pictures don't load fully:
2nd brood female, Switzerland, July 2009
2nd brood female, Switzerland, July 2009
Female, Switzerland, July
2009
Female underside, Suffolk,
UK, August 2012
Female upperside, Suffolk, UK, August 2012
Egg, April 2020, UK
2nd instar caterpillar on ivy, August 2020
Freshly moulted 4th instar caterpillar on ivy, August 2020
4th instar caterpillar on ivy, August 2020
Older 4th instar caterpillar on ivy, August 2020 (photographed at night)
Distribution
Found all over Europe except
for the very
far north and the northern tip of Scotland, this is one of our most
familiar butterflies and a welcome harbinger of spring. It is a
characteristic species of towns and gardens, where it famously thrives
on holly in the spring and ivy in the summer. However, it will also
take a huge variety of other herbs, bushes and trees and this is
doubtless one of the keys to its success. That said, it is not always
common. Its numbers fluctuate in a regular fashion, building up over a
series of years and then suddenly crashing. This attributed to its
relationship with the parasitic wasp Listrodomus
nycthemerus. When the host is plentiful, parasite numbers
explode and wipe out large numbers of the butterfly.
Identification is easy. Males are sky blue above with a chequered forewing border and a neat, narrow, black margin, slightly broader at the apex of the forewing. Females of the first brood are the same blue but with a much broader dark border. In the second brood this border is still broader, extending down the leading edge of the forewing, and the ground colour is generally duller. Males of the second brood are similar to those of the first brood. The underside of both sexes is white with black spots. The spots on the forewing are characteristically elongated, making this species instantly separable from superficially similar butterflies.
Because of their eclectic choice of hostplant, holly blues can be found in all sorts of habitat, though they are rarely far from trees or bushes. I have found them sharing a patch with Lorquin's blues in southern Andalucia, skitting around with Camberwell beauties in the hottest parts of the Swiss Rhône Valley and sitting on forest oaks with purple hairstreaks in the UK. They are always a joy to see. Both sexes enjoy nectaring and males in particular will often join groups of other blues to take minerals on damp paths.
Holly blues hibernate as
pupae, hidden
away on or near the ground near - or deep within - their foodplant.