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 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.
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.
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.
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.
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.
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