The Holly Blue is primarily found in the southern half of the British Isles, and is a frequent visitor to gardens. This species is renowned for fluctuating wildly in numbers, forming a predictable cycle over a few years, believed to be caused by parasitism from the wasp Listrodomus nycthemerus whose sole host is the Holly Blue. The wasp lays its eggs in Holly Blue larvae, with a single adult wasp eventually emerging from the Holly Blue pupa. In England and Wales this species is widespread and common, south of a line running from Cumberland in the west to County Durham in the east. This species is also found on the Isle of Man and throughout Ireland, but is absent from Scotland except as a scarce vagrant.
Celastrina argiolus ssp. argiolus
The species was first defined in Linnaeus (1758) as shown here (type locality: Europe). The nominate subspecies is not found in the British Isles.
Celastrina argiolus ssp. britanna
This subspecies was first defined in Verity (1919) as shown here (type locality: Woodford, Epping Forest, Essex, England). The population in the British Isles is represented by this subspecies. Males of the spring and summer brood are similar in appearance, but females of the summer brood have a much broader dark band on the upperside of the forewings than those of the spring brood.
Photo © Alan Thornbury
There are two broods each year, although there may be only one brood in the north. Adults from overwintering pupae emerge as early as the first week of April in a typical year, with the next generation emerging at the end of July and early August.
The chart(s) above have been correlated with the phenology plot below, taken from the UK Butterfly Monitoring Scheme. The blue line gives average counts over the full data set from 1976 to date, and the red line gives the average for the last year.
This butterfly is found in many different types of habitat, including gardens, churchyards, woodland, parks, and anywhere its foodplants and nectar sources can be found.
The primary larval foodplants are Holly (Ilex spp.) and Ivy (Hedera helix). Bramble (Rubus fruticosus), Dogwoods (various) (Cornus spp.), Gorses (various) (Ulex spp.), Snowberries (various) (Symphoricarpos spp.) and Spindle (Euonymus europaeus) are also used.
Adults feed primarily on Bramble (Rubus fruticosus), Bugle (Ajuga reptans), Buttercups (Ranunculus spp.), Forget-me-not (Myosotis spp.), Holly (Ilex spp.), Honeydew / Sap (), Ivy (Hedera helix), Privet (Ligustrum vulgare), Thistles (Cirsium spp. and Carduus spp.) and Water Mint (Mentha aquatica).
The adults are most easy to identify when at rest, since their undersides are distinctive among the blues found in the British Isles, with the possible exception of the Small Blue, which is much scarcer (and, as its name implies, much smaller). The male and female are distinguished by their uppersides, where the forewings of the female have broad black borders that are absent in the male. However, the adults only tend to open their wings in weak sunshine. Second brood females generally have broader black borders than first brood females.
A particular characteristic of this blue is that it will fly high off the ground, distinguishing it from other blues. In this respect, they are more similar in behaviour to a hairstreak.
Both sexes visit a variety of nectar sources such as Bramble, Holly and Forget-me-not. However, they do seem to have a preference for honeydew rather than nectar. The males will also come down to the ground to take salts and minerals from damp mud and animal waste.
Description to be completed. Click here to see a full list of aberrations for this species.
The white eggs are laid singly at the base of unopened flower buds of the foodplant. Eggs laid in spring are typically laid on Holly, whereas the summer eggs are typically laid on Ivy. And so the Ivy Blue would be an equally-appropriate name for this species! In this respect, the Holly Blue is unique in the British Isles, where the different broods use different foodplants. In good years, the eggs can be relatively easy to find on the foodplant and hatch in around 2 weeks.
The larva is extremely well camouflaged, and is usually a plain green colour, although some larvae may also have areas that are light pink. The larva is most-easily found by looking for damage to the developing flower buds, where it may usually be found attached to a neighbouring bud. The larva bores a hole in the side of the flower bud and scoops out the content, leaving a succession of empty flower buds, each with an access hole, in its wake. The larva has 3 moults in total.
The larva leaves the foodplant to pupate on or near the ground, and turns mauve in colour prior to pupation. The larva spins a very fine silken girdle to attach itself to the chosen pupation site. Pupae from the spring generation emerge in 2 to 3 weeks, whereas those formed in late summer overwinter.
Description to be completed.
Description to be completed.
Click here to see the distribution of this species overlaid with specific site information. Alternatively, select one of the sites listed below.
|Arnside Knott, Arthur's Seat, Aspal Close, Attenborough Nature Reserve, Banstead Woods, Bedfont Lakes Country Park LNR, Blackrock, Bohill Forest, Bovey Valley Woodlands, Bryncelyn Hall, Cork City, Cuerden Valley Park, Curraghbinny Wood, Devil's Ditch, Durlston NNR, Enniskerry Glen, Fleam Dyke, Forest Farm Meadows, Gait Barrows, Horsenden Hill, Hounslow Heath LNR, Howardian Local Nature Reserve, Latton Woods, Laughton Common Wood, Leighton Moss, Mansmead wood, Mayford Pond, Meanwood Park, Midgham Lakes, Mill Hill, Moss Field, Old Down, Basingstoke, Orton Longueville, Parc Penallta, Pulborough Brooks (RSPB), Rookery, St. Stephen's Green, Strumpshaw Fen, Sun Lane Nature Park, Thurlbear Quarrylands, Uffmoor Wood, Viking Field/LesleySears, Warton Crag, Willesley Wood|
The population trend of this delightful butterfly is one of a marked increase. It has also spread northward. It is not, therefore, considered a species of conservation concern.
From The State of Butterflies in Britain and Ireland and the UK Biodiversity Action Plan (UK BAP) (2007 review).
The following links provide additional information on this butterfly.
The species description provided here references the following publications:
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