both Cumnor Hill, Oxford, England
The holly blue has pale silver-blue wings spotted with pale ivory dots. Seitz describes it "Male above shining violet blue, only the apical portion of the costal margin being minutely edged with white. The female has both wings broadly bordered with dark, the margin of the hindwing bearing vestiges of ocelli. Underside silver-white, in the disc a row of black dots, some of which are elongate, and before the margin blackish shadowy dots. Egg very flat, whitish. Larva green or brown, marked with yellowish white, bearing catenulate stripes on the back, on segment 7 a gland to attract ants; head brown. On Ivy, Ilex, Evonymus, Rhamnus, Robinia, Genista, Spartium, Astragalus, Rubus, Erica, Pyrus and many other plants; in Europe visited usually by ants of the genus Lasius; in June and the autumn. Pupa mostly fastened to the underside of a leaf, ochreous with brown spots and markings. The butterflies in the spring and again in July, occasionally a third time at the end of August and in September, everywhere common, particularly at the flowers of ivy and brambles." In Europe, the first generation feeds mainly on the holly species Ilex aquifolium but the second generation uses a range of food plants.
The holly blue is the national butterfly of Finland.
This species was originally described as Papilio argiolus by Carl Linnaeus in 1758, and refers to the examples flying in Europe. In their monograph on the Lycaenopsis group of polyommatine genera, Eliot & Kawazoe, 1983, list 14 taxa as valid subspecies names, plus many further synonyms to which they accord lesser status. According to Eliot & Kawazoe, 1983, these 14 subspecies are divided into four groups as follows:
Palaearctic & North African
South and South-East Asian
North and Central American
In India, C. argiolus is known as the hill hedge blue. In North America, the ladon group of subspecies are known as the spring azure. In addition the name echo blue is used for the western subspecies, C. a. echo.
female laying egg, Bulgaria
- Beccaloni, G.; Scoble, M.; Kitching, I.; Simonsen, T.; Robinson, G.; Pitkin, B.; Hine, A.; Lyal, C., eds. (2003). "Celastrina argiolus". The Global Lepidoptera Names Index. Natural History Museum. Retrieved April 20, 2018.
- Seitz, A. ed. Band 1: Abt. 1, Die Großschmetterlinge des palaearktischen Faunengebietes, Die palaearktischen Tagfalter, 1909, 379 Seiten, mit 89 kolorierten Tafeln (3470 Figuren)
- Butterfly Conservation A-Z of butterflies Archived 2010-06-20 at the Wayback Machine
- "Finland's national butterfly is the holly blue - Suomi 100". suomifinland100.fi. Archived from the original on 2018-06-19. Retrieved 2017-08-01.
- Evans, W.H. (1932). The Identification of Indian Butterflies (2nd ed.). Mumbai, India: Bombay Natural History Society. pp. 221–226, ser no H21.24.
- Tveten, John & Gloria (1996). Butterflies of Houston & southeast Texas. Austin: University of Texas Press. p. 98. ISBN 978-0292781436.
- Powell & Hogue (1980). California Insects. California Natural History Guides. p. 240. ISBN 0520037820.
- Beccaloni, George; Scoble, Malcolm; Kitching, Ian; Simonsen, Thomas; Robinson, Gaden; Pitkin, Brian; Hine, Adrian; Lyal, Chris. "The Global Lepidoptera Names Index (LepIndex)". Natural History Museum, London. Retrieved 2016-10-15.
- Eliot, J. N. and Kawazoe, A., 1983. Blue butterflies of the Lycaenopsis group: 1-309, 6 pls. London.
- Evans, W.H. (1932). The Identification of Indian Butterflies (2nd ed.). Mumbai, India: Bombay Natural History Society.
- Willmott, Ken and Freed, Tim (1999). The Holly Blue Butterfly. Butterfly Conservation, Colchester, UK, 20p. ISBN 0-9522602-7-1.
- "Celastrina argiolus". Integrated Taxonomic Information System. Retrieved 6 February 2006.
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