Holly Blue (Celastrina argiolus)
Species

Male. Taken at Abingdon, Oxon., on May 9th 2015.
(1/640th sec at f10. Approx 3x lifesize. © David Hastings)

Male underside. Taken at Dry Sandford Pit, Oxon., on April 30th 2019.
(1/800th sec at f14. Approx 3x lifesize. © David Hastings)

Female. Taken at Bagley Wood, Oxon., on April 23rd 2011.
(1/100th sec at f10. Approx 3x lifesize. © David Hastings)

Female underside. Taken at Abingdon, Oxon., on April 30th 2019.
(1/1000th sec at f14. Approx 3x lifesize. © David Hastings)

Description

Wing span: 26 - 34 mm

This butterfly is often seen in gardens, flying around shrubs in spring and again in summer. Both sexes have blue uppersides; females have black borders on both pairs of wings. In second-brood females the borders are wider. Both sexes have pale blue undersides with black dots. They usually keep their wings closed while at rest.

The Holly Blue is widespread in southern and central England, becoming more patchy in Wales and northern England.

It can be found in woods and along hedges where there is plenty of Holly and Ivy nearby. It can also be found in churchyards, parks and gardens.

There are typically two emergences each year, although there may be only one in the north, and sometimes a third one in the south in hot years. Adults from overwintering pupae can emerge as early as the first week of April, with the next generation emerging at the end of July, and the third (if present) in September.

The main foodplants are Holly (in spring) and Ivy (in summer). Bramble, Dogwoods, Gorses, Snowberries and Spindle are also used.

Adults feed primarily on Bramble, Bugle, Buttercups, Forget-me-not, Holly, Honeydew, Sap, Ivy, Privet, Thistles and Water Mint.

This species is renowned for fluctuating wildly in numbers, forming a predictable cycle over a few years. This cycle is caused by parasitism by the wasp Listrodomus nycthemerus. The wasp lays its eggs in the larva of the Holly Blue, with a single adult wasp eventually emerging from the Holly Blue pupa.

This species is of Least Concern on the UK list.

Sightings

03-Jun-2019 : Otmoor, Oxon (1)
03-Jun-2019 : Whitecross Green Wood, Oxon (2)
02-Jun-2019 : Barton Fields, Abingdon, Oxon (1)
01-Jun-2019 : Ardley Quarry, Oxon (3)
01-Jun-2019 : Bucknell Wood, Northants (1)
01-Jun-2019 : Garden, Abingdon, Oxon (1)
30-May-2019 : Garden, Abingdon, Oxon (1)
16-May-2019 : Garden, Abingdon, Oxon (2+)
15-May-2019 : Garden, Abingdon, Oxon (2+)
15-May-2019 : Allotment, Abingdon, Oxon (1)
14-May-2019 : Garden, Abingdon, Oxon (2+)
13-May-2019 : Garden, Abingdon, Oxon (1)
12-May-2019 : Ivinghoe Beacon, Bucks (1)
11-May-2019 : Radley Lakes, Oxon (2)
11-May-2019 : Garden, Abingdon, Oxon (2)
11-May-2019 : Abingdon, Oxon (4)
10-May-2019 : Garden, Abingdon, Oxon (3)
07-May-2019 : Garden, Abingdon, Oxon (2)
30-Apr-2019 : Garden, Abingdon, Oxon (2+)
30-Apr-2019 : Allotment, Abingdon, Oxon (1)
30-Apr-2019 : Dry Sandford Pit, Oxon (3)
29-Apr-2019 : Standlake Common, Oxon (3)
29-Apr-2019 : Garden, Abingdon, Oxon (2+)
26-Apr-2019 : Farmoor Reservoir, Oxon (1)
26-Apr-2019 : Garden, Abingdon, Oxon (2)
25-Apr-2019 : Garden, Abingdon, Oxon (2)
24-Apr-2019 : Garden, Abingdon, Oxon (1)
23-Apr-2019 : Garden, Abingdon, Oxon (4+)
22-Apr-2019 : Garden, Abingdon, Oxon (6+)
22-Apr-2019 : Hackpen Hill, Oxon (1)
21-Apr-2019 : Garden, Abingdon, Oxon (4+)
20-Apr-2019 : Garden, Abingdon, Oxon (6+m)
20-Apr-2019 : Dry Sandford Pit, Oxon (1f)
19-Apr-2019 : Aston Upthorpe Downs, Oxon (1)
19-Apr-2019 : Garden, Abingdon, Oxon (6+)
18-Apr-2019 : Garden, Abingdon, Oxon (2m)
17-Apr-2019 : Garden, Abingdon, Oxon (2m)
30-Mar-2019 : Garden, Abingdon, Oxon (1m)
29-Mar-2019 : Garden, Abingdon, Oxon (2m)

25-Aug-2018 : Standlake Common, Oxon (1)
16-Aug-2018 : Farmoor Reservoir, Oxon (1)
14-Aug-2018 : Garden, Abingdon, Oxon (1)
09-Aug-2018 : Sandford Brake, Oxon (1)
05-Aug-2018 : Garden, Abingdon, Oxon (1)
04-Aug-2018 : Garden, Abingdon, Oxon (1)
03-Aug-2018 : Garden, Abingdon, Oxon (1)
02-Aug-2018 : Garden, Abingdon, Oxon (1)
31-Jul-2018 : Garden, Abingdon, Oxon (2)
30-Jul-2018 : Garden, Abingdon, Oxon (2)
29-Jul-2018 : Garden, Abingdon, Oxon (1)
26-Jul-2018 : Garden, Abingdon, Oxon (1)
23-Jul-2018 : Vercors Natural Park, France
21-Jul-2018 : Vercors Natural Park, France
20-Jul-2018 : Vercors Natural Park, France
19-Jul-2018 : Vercors Natural Park, France
16-Jul-2018 : Garden, Abingdon, Oxon (1)
15-Jul-2018 : Garden, Abingdon, Oxon (1)
14-Jul-2018 : Watlington Hill, Oxon (1)
11-Jul-2018 : Garden, Abingdon, Oxon (2+)
08-Jul-2018 : Garden, Abingdon, Oxon (2)
07-Jul-2018 : Besselsleigh Wood, Oxon (1)
07-Jul-2018 : Garden, Abingdon, Oxon (1)
05-Jul-2018 : Garden, Abingdon, Oxon (2)
04-Jul-2018 : Garden, Abingdon, Oxon (2+)
01-Jul-2018 : Garden, Abingdon, Oxon (1)
19-Jun-2018 : Garden, Abingdon, Oxon (1)
11-Jun-2018 : Garden, Abingdon, Oxon (1)
03-Jun-2018 : Stockbridge Down, Hants (1)
03-Jun-2018 : Garden, Abingdon, Oxon (1)
01-Jun-2018 : Garden, Abingdon, Oxon (2)
28-May-2018 : Garden, Abingdon, Oxon (1)
27-May-2018 : Garden, Abingdon, Oxon (2)
26-May-2018 : The Holies, Berks (1)
20-May-2018 : Garden, Abingdon, Oxon (1)
17-May-2018 : Sandford Brake, Oxon (3m)
17-May-2018 : Garden, Abingdon, Oxon (1m)
15-May-2018 : Garden, Abingdon, Oxon (2m,1f)
13-May-2018 : Garden, Abingdon, Oxon (1m)
12-May-2018 : Garden, Abingdon, Oxon (1)
08-May-2018 : Garden, Abingdon, Oxon (2)
07-May-2018 : Garden, Abingdon, Oxon (2)
06-May-2018 : Allotment, Abingdon, Oxon (1)
06-May-2018 : Garden, Abingdon, Oxon (1)
26-Apr-2018 : Bagley Wood, Oxon (3m)
22-Apr-2018 : Standlake Common, Oxon (2m)
21-Apr-2018 : Allotment, Abingdon, Oxon (1m)
21-Apr-2018 : Garden, Abingdon, Oxon (1m)
20-Apr-2018 : Garden, Abingdon, Oxon (2m)
19-Apr-2018 : Garden, Abingdon, Oxon (1m)
14-Apr-2018 : Garden, Abingdon, Oxon (1)

12-Aug-2017 : Dersingham Bog, Norfolk (1)
29-Jul-2017 : Garden, Abingdon, Oxon (1)
18-Jul-2017 : Greenham Common, Berks (1)
08-Jul-2017 : Bayworth, Oxon (1)
04-Jul-2017 : Garden, Abingdon, Oxon (1)
02-Jul-2017 : Fence Wood, Berks (1m)
08-Jun-2017 : Paklenica National Park, Croatia
21-May-2017 : Garden, Kidlington, Oxon (1m,1f)
18-May-2017 : University Parks, Oxford, Oxon (1)
14-May-2017 : Whelford Pools, Glos (2)
10-May-2017 : Garden, Abingdon, Oxon (1)
07-May-2017 : Garden, Abingdon, Oxon (1)
07-May-2017 : Lardon Chase, Berks (3)
07-May-2017 : Allotment, Abingdon, Oxon (1)
07-May-2017 : Aston Upthorpe Downs, Oxon (1)
02-May-2017 : Dry Sandford Pit, Oxon (3m)
01-May-2017 : Garden, Abingdon, Oxon (1)
30-Apr-2017 : Allotment, Abingdon, Oxon (1)
22-Apr-2017 : Garden, Abingdon, Oxon (1m)
22-Apr-2017 : Bagley Wood, Oxon (1)
21-Apr-2017 : Garden, Abingdon, Oxon (1m)
18-Apr-2017 : Garden, Abingdon, Oxon (1m)
17-Apr-2017 : Garden, Abingdon, Oxon (1m)
15-Apr-2017 : Garden, Abingdon, Oxon (1m)
11-Apr-2017 : Garden, Abingdon, Oxon (1m)
09-Apr-2017 : Aston Rowant NNR, Oxon (2)
08-Apr-2017 : Allotment, Abingdon, Oxon (1)
08-Apr-2017 : Garden, Abingdon, Oxon (1)

23-Aug-2016 : Garden, Abingdon, Oxon (1)
16-Aug-2016 : Garden, Abingdon, Oxon (2)
13-Aug-2016 : Garden, Abingdon, Oxon (2m)
12-Aug-2016 : University Parks, Oxford, Oxon (1)
09-Aug-2016 : Garden, Abingdon, Oxon (1)
07-Aug-2016 : Otmoor, Oxon (1)
07-Aug-2016 : Garden, Abingdon, Oxon (1)
06-Aug-2016 : Fence Wood, Berks (1)
06-Aug-2016 : Garden, Abingdon, Oxon (1)
03-Aug-2016 : University Parks, Oxford, Oxon (1)
31-Jul-2016 : Garden, Abingdon, Oxon (1)
28-Jul-2016 : St Giles' Churchyard, Oxford (1)
26-Jul-2016 : Garden, Abingdon, Oxon (2)
23-Jul-2016 : Garden, Abingdon, Oxon (1)
14-Jul-2016 : Garden, Abingdon, Oxon (1)
09-Jun-2016 : University Parks, Oxford, Oxon (1m)
05-Jun-2016 : Garden, Abingdon, Oxon (1)
28-May-2016 : Garden, Abingdon, Oxon (1)
28-May-2016 : Ardley Quarry, Oxon (1m)
27-May-2016 : Garden, Abingdon, Oxon (1)
27-May-2016 : Dry Sandford Pit, Oxon (1)
24-May-2016 : Garden, Abingdon, Oxon (2)
22-May-2016 : Goring Railway Bridge, Oxon (1)
22-May-2016 : Aston Upthorpe Downs, Oxon (1)
15-May-2016 : Garden, Abingdon, Oxon (2m)
15-May-2016 : Hitchcopse South Sandpit, Oxon (2)
15-May-2016 : Dry Sandford Pit, Oxon (4m,1f)
14-May-2016 : Garden, Abingdon, Oxon (1m)
08-May-2016 : Garden, Abingdon, Oxon (2m)
08-May-2016 : Whelford Pools, Glos (1m)
07-May-2016 : Garden, Abingdon, Oxon (1m)
06-May-2016 : Garden, Abingdon, Oxon (1m)
05-May-2016 : Dry Sandford Pit, Oxon (1)
04-May-2016 : Garden, Abingdon, Oxon (1m)

12-Sep-2015 : Radley Lakes, Oxon (1)
07-Sep-2015 : Garden, Abingdon, Oxon (1)
29-Aug-2015 : Lardon Chase, Berks (1)
29-Aug-2015 : Garden, Abingdon, Oxon (1)
12-Aug-2015 : University Parks, Oxford, Oxon (1)
11-Aug-2015 : Garden, Abingdon, Oxon (1)
09-Aug-2015 : Garden, Abingdon, Oxon (2)
08-Aug-2015 : Garden, Abingdon, Oxon (3m)
08-Aug-2015 : Dry Sandford Pit, Oxon (1f)
02-Aug-2015 : Garden, Abingdon, Oxon (2)
02-Aug-2015 : Otmoor, Oxon (2)
30-Jul-2015 : Garden, Abingdon, Oxon (1)
29-Jul-2015 : Garden, Abingdon, Oxon (2)
25-Jul-2015 : Nr Dobrinishte, Bulgaria
24-Jul-2015 : nr Kirilova polyana, Bulgaria
23-Jul-2015 : Mesta River fishponds, Bulgaria
22-Jul-2015 : Kresna Gorge, Bulgaria
22-Jul-2015 : nr Lilyanovo, Bulgaria
22-Jul-2015 : Melnik, Bulgaria
18-Jul-2015 : Garden, Abingdon, Oxon (1)
14-Jul-2015 : Garden, Abingdon, Oxon (1)
11-Jun-2015 : University Parks, Oxford, Oxon (1)
07-Jun-2015 : Garden, Abingdon, Oxon (1)
04-Jun-2015 : University Parks, Oxford, Oxon (1f)
30-May-2015 : Garden, Abingdon, Oxon (1m)
28-May-2015 : University Parks, Oxford, Oxon (4m)
26-May-2015 : Garden, Abingdon, Oxon (1m)
21-May-2015 : University Parks, Oxford, Oxon (3)
17-May-2015 : Stockbridge Down, Hants (1f)
16-May-2015 : Ivinghoe Beacon, Bucks (3)
13-May-2015 : University Parks, Oxford, Oxon (4m)
12-May-2015 : Garden, Abingdon, Oxon (1)
09-May-2015 : Garden, Abingdon, Oxon (1m)
04-May-2015 : Aston Upthorpe Downs, Oxon (1)
03-May-2015 : Garden, Abingdon, Oxon (1m)
30-Apr-2015 : Arne, Dorset (1)
25-Apr-2015 : Ardley Quarry, Oxon (1)
23-Apr-2015 : University Parks, Oxford, Oxon (1)
21-Apr-2015 : Dry Sandford Pit, Oxon (1)
21-Apr-2015 : Garden, Abingdon, Oxon (1)
18-Apr-2015 : Aston Upthorpe Downs, Oxon (1m)