Holly blue

The common name Holly blue is derived from the association of the larval stage with the Holly tree. ==Description==

The holly blue has violet blue wings, and pale silver-blue under-wings spotted with black dots. Seitz describes it: In Europe, the larvae of the first generation (the spring generation) feed mainly on the holly species Ilex aquifolium (the flower buds, berries, and leaves), but the second generation (the summer generation) uses a range of food plants including Spindle, Dogwoods, Ivy, and Bramble. The wingspan is around 2.6 to 3.4cm. The Holly blue usually perches with it's wings almost fully closed or around 90 degrees. The holly blue is the national butterfly of Finland. ==Taxonomy==

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: ;The argiolus group Palaearctic & North African • C. a. argiolus • C. a. bieneri • C. a. hypoleuca :=paraleuca Rober • C. a. mauretanica :=algirica Oberthur ;The kollari group South and South-East Asian • C. a. iynteana :=sikkima Moore :=victoria Swinhoe :=herophilus Fruhstorfer :=cition Fruhstorfer :=bothrinoides Chapman :=puspargiolus Chapman :=albocaeruloides Chapman • C. a. kollari :=kasmira Moore :=coelestina Kollar :=trita Swinhoe ;The ladonides group Far Eastern • C. a. caphis :=crimissa Fruhstorfer • C. a. ladonides :=levettii Butler :=sachalinensis Esaki :=heringi Kardakoff • C. a. sugurui ==Range==

Found throughout Eurasia. It is particularly common in the south of Great Britain. In South Asia, it occurs from Chitral in Pakistan to Kumaon in India. ==Population cycle==

The holly blue is subject to marked population cycles which appear to be caused by interactions with the parasitoid ichneumon wasp Listrodromus nycthemerus. The wasp lays an egg on a holly blue caterpillar, inserting the egg into the caterpillar's body and the adult wasp emerges from the chrysalis, killing the chrysalis before its emergence. The population of the butterfly is tracked by that of the wasp, when butterfly populations are low the wasp population falls and this allows the butterfly population to increase and the population of L. nycthemerus can increase as there are more hosts available to be parasitised. As more caterpillars are parasitised the butterfly population crashes. ==See also==

Holly blue (Celastrina argiolus) female laying egg Bulgaria.jpg|female laying egg, Bulgaria File:Celastrina argiolus egg.jpg|Egg File:Lycaenidae - Celastrina argiolus-6.JPG|Imago File:0 Azuré des nerpruns (♀) - Celastrina argiolus - Havré (1).JPG|Female File:Celastrina Argiolus.jpg|Bottom sides of the wings Holly blue (Celastrina argiolus) male underside.jpg|Male ==References==