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Holly Blue

Photograph by: 
Peter Orchard

The most likely blue to be seen in gardens and not uncommon across Dorset


  • Holly blue: the holly and the ivy ...

    Post date: Wednesday, 7 May, 2014 - 00:00

    Is the holly blue (Celastrina argiolus) not an adorable little butterfly? Totally exquisite when seen close up with an amazing silvery under wing and bright blue upper wings although the females have black markings on the upper wings which can be confusing!

    The holly blue is also a fascinating creature. The insect over winters as a pupae, usually hidden in amongst Ivy. In April they emerge, mate and lay their eggs on holly flowers. First broods will be gone by early June and then the eggs from the first brood (laid on holly) emerge, mate and lay their eggs on ivy. The larvae pupate and over winter in amongst the ivy and so the cycle continues. Second broods are only briefly on the wing in late July/early August.

    Most blues are grassland species but the holly blue is, because of its affinity to the holly and the ivy, more at home in woodlands, shrubby areas and gardens. It is the most likely blue you will see in your garden in most areas.


  • Holly Blue in Dorset: what your tweets tell us ...

    Post date: Monday, 29 April, 2019 - 21:18

    The holly blue is the most likely blue butterfly you will see in your garden; that is if you have a garden and where that garden is of course! It favours shrubby areas including woodland but it is well suited to parks, churchyards, gardens and the like. It has two broods each year and the early females lay their eggs of the flowers of holly whilst the second brood females lay their eggs mainly on ivy. Numbers seen each year vary considerably. They are subject to paratisation by a species of wasp, Listrodomus nychemerus, and if there are a lot of holly blues then the wasp will do well and reduce the population of the holly blue but then with less holly blue caterpillars to lay eggs in to the wasp declines meaning the holly blue recovers and so the cycle goes on. 

    The first brood of holly blue emerge quite early in the year, as early as March in good years, and they fly until the end of May or early June. After a short gap the second broog emerge and can be seen until the end of September. That is what the textbooks say but the twenty nine reports of holly blue in the Nature of Dorset database for 2017 and 2018 are not wholly in line with this. There are a small number of reports starting in week 12 at the end of March and then the reports are fairly consistent through until week 20 at the end of May just as the books say. The second brood reports start in week 27 which is well into July and continue to week 34 in mid September and it is in week 34 that reports reach a peak. However, there were two surprise reports in weeks 40 and 41 in 2018 which is well into October so could that be a third brood here in the south?

    There are reports from twenty four sites and they are widespread across the county; I cannot see any real pattern that would seem habitat related. It is noticeable that virtually all of the reports come from the east of a vertical line from Portland to Sherborne but this may just be a lack of recorders in the west of the county.

Common Name Holly Blue
Scientific Name Celastrina argiolus
Species Group Lycaenid Butterflies Blues and Hairstreaks
Interest Level
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Identification Notes
Primary Habitat
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Additional Identification Notes
Similar Species

The records for this species have been organised into reports, charts, maps and photos. Click a pic below to see the detail:

Notebook Distribution Map Sites List Some Charts Some Photographs Recent Records Guidance Notes

To see related species click here: 

Lycaenid Butterflies Blues and Hairstreaks