Usually the first blue to be seen on the wing, as early as late March. Its population goes through cycles, probably because it is parasitised by an ichnuemon wasp: as the predator gains ground Holly Blue numbers reduce then, for lack of food, the parasite declines, allowing the butterfly to increase in number again.
Where to see
- Habitat: Unlike the other blues, the Holly Blue is not limited to a very specific habitat: its caterpillar feeds on a range of bushes and the adult butterflies can fly good distances. It will live in hedgerows, woods and gardens.
- Caterpillar foodplants: Holly (for the first brood), Ivy (for the second brood), Gorse, Dogwood, Spindle, Alder Buckthorn.
- Best places: This is a widespread butterfly, but you could particularly try: Cashmoor, Clubmens Down, Ballard Down, Townsend Quarry, Stour Valley, Mude Valley, Redhill, Milldown
Distribution map
Holly Blue was recorded from these 1km squares in Dorset (2015-19).
- Key:
- 1 record
- 2-9 records
- 10+ records
When to see
Double-brooded, with a possible partial third brood in the south of the U.K. (1) late March to late June, (2) late July into September, (3) October (not every year)
Sightings by month (last 5 years)*
This year and last*
What to look for
The Holly Blue is rarely seen with wide open wings, so you are more likely to be able to get a good look at the underwings, which is how it is best identified anyway. It has pale blue underwings, with black dots/splodges scattered over the whole area and no orange marks.
The only other blue with underwings remotely like it is the Small Blue, but this is a tiny butterfly and much rarer than the Holly, and the background colour is more silver.
The upperwings on both sexes is blue. The male is possible to confuse with the Common Blue if only seen from above, but the female is the only blue with a wide black band round the top of her forewings; this band is wider in second brood females than first brood. Also, while the fringes around the upper sides of the Common Blue are pure white, in the Holly Blue, the forewings of fresh specimens are chequered with black lines running across them.
It is much more likely to be seen flying high than any other blue; the others tend to hug the ground more, though this is not a hard rule. The exception is in very warm and dry weather, when several Holly Blues may be seen together, drinking from the salts in the mud puddles.
Time of year is also helpful: if a blue butterfly is seen in April, it will be a Holly Blue.
Photo gallery
Click thumbnails to view full-size images.
Holly Blue. The underside has a pale blue background peppered with balck spots. Photo: Brian Arnold.
Holly Blue. You can tell this is a male by the lack of a broad black band on the upper wings. Photo: Ken Dolbear.
Holly Blue. The extensive broad black band on the edge of the wings shows this to be a second brood female. Photo: Mel Bray
First brood female with a less extensive black band. The upper wing white fringe is chequered with black cross bands, unlike the Common Blue. Photo: Lawrie de Whalley
Holly Blues mating. Photo: John Van Crugten.
Holly Blues. The exception to the rule that Holly Blues fly at hedge height is when several gather around mud to probe for minerals.
Holly Blue caterpillar. Photo: Dean Morley
Holly Blue egg. Photo: Gary Holderness