Holly Blue (Celastrina argiolus) – ID Guide

The Holly Blue is a beautiful and delicate species of butterfly, it is not as common as the Common Blue Butterfly, but is also a high flying species, which may contribute to a lack of records.

The beautiful and highflying Holly Blue – Oisín Duffy

The Holly Blue is another small species (35mm wing span) and is quite similar to the Common Blue, although in my experience Holly Blues have a habit of being slightly smaller. The species has a beautiful blue colouration on the topside of the wings and distinctive black wing tips, the female of the species has much more prominent black wing tips, while the males are very subtle, almost an edging.

Topside of the Holly Blue – Oisín Duffy

The underside of the Holly Blue is a powdery baby blue colour, almost ranging into silver and has a number of black spots. The main difference between the Holly Blue and the Common Blue comes from the underside. While the Common Blue has elaborate orange marking along the wing margin, the Holly Blue has no orange at all. If you’re lucky enough to get the species to sit, then this should be very noticeable. It’s also very worthwhile looking up (above head height) as this is the preferred flying area for the Holly Blue.

Underside of the Holly Blue, notice how there’s no orange markings, which is a distinguishing feature in comparison to the Common Blue – Oisín Duffy

The distribution of the Holly Blue has a slight south easterly leaning. It is however also found in Clare and Galway and many other counties. Lack of habitat may be one of the reasons why the distribution appears so limited or perhaps the elusive nature of the butterfly means that it is under recorded. It can be found in woodlands, hedgerows and sometimes even gardens.

Holly (Ilex aquifolium) – Oisín Duffy

The larval foodplant of the Holly Blue is split between two plant species, Holly (Ilex aquifolium) and Ivy (Hedera helix), other plants can also be used. In Spring, Holly is chosen and by the time the next brood comes to lay eggs they will be looking for Ivy. This can explain why they are flying noticeably higher than some of our other native species of butterflies. If your larval foodplant is up high you’ll need to fly high to lay eggs and find potential mates.

Ivy (Hedera helix) – Oisín Duffy

Cheat Sheet – (TLDR Version):

Name: Holly Blue (Celastrina argiolus)

Larval Foodplant: Holly (Ilex aquifolium) and Ivy (Hedera helix)

Distribution: Scattered distribution throughout the country, slightly more common in south and east of the country (but does occur elsewhere), may be under recorded due to its highflying nature.

When: From April to May and then again from July to September.

If you’re interested in learning more about butterflies why not take part in the Irish Butterfly Monitoring Scheme, the national scheme for recording and monitoring butterfly species in Ireland.

If anyone out there has any questions or suggestions regarding this piece or maybe regarding future pieces, feel free to get in touch through Twitter.

About Oisín Duffy 23 Articles
Oisín Duffy is an ecologist and environmental educator with a special interest in the Flora of Ireland and Pollinators. He is the photographer and co-author of Biodiversity Ireland’s identification guide on “Trees and Shrubs”. He has a BA from NUIG and an MSc from NUIG and UL. Oisín is an active biological recorder, and current Botanical Society of Britain and Ireland (BSBI) Vice-county recorder for East Donegal (H34) and participates in a number of recording schemes run by the National Biodiversity Data Centre (NBDC), Bat Conservation Ireland (BCI) and others. In 2016, Oisín worked in conjunction with the National Biodiversity Data Centre to develop a plant monitoring scheme for Ireland. During the Summer of 2016, he toured Ireland giving workshops for the Irish Butterfly Monitoring Scheme. His most recent work has been as a photographer and author of the “Wildflowers in South Armagh”.

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