UK Butterflies

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Purple Hairstreak

Favonius quercus

fav-OH-nee-us KWARE-cuss

Wingspan
♂ 33 - 40 mm, ♀ 31 - 38 mm

Checklist Number
61.004

Purple Hairstreak

Favonius quercus

fav-OH-nee-us KWARE-cuss

Wingspan
♂ 33 - 40 mm, ♀ 31 - 38 mm

Checklist Number
61.004


The Purple Hairstreak is our commonest hairstreak, and may be found in oak woodland throughout southern Britain, and more locally elsewhere. It is often difficult to locate, due to its habit of flying in the tree canopy, where it feeds on honeydew. However, the adults are occasionally seen basking at lower levels, on various small trees, shrubs and bracken. This butterfly is found across southern England and Wales, with scattered colonies further north. It is also found in parts of Ireland, mainly between Wicklow and South Kerry. This species is not found in the Isle of Man.

This species was first defined in Linnaeus (1758) as shown here (type locality: Not stated).

Description to be completed.

The distribution data (2000-2009) has been made available through the generosity of Butterfly Conservation and any subspecies distribution is taken from Riley (2007). Click here to see the distribution of this species together with site information overlaid.

This butterfly is primarily found in woodland containing oak trees, the foodplant of the larva. However, the species can be found in any location where oaks occur, including lanes, parks, and other urban areas.

The status of this species is relatively-stable and numbers have even increased in some areas. As such, it is not a species of conservation concern.

The table below shows the occurrence (distribution) and abundance (population) trends, using information from The State of the UK's Butterflies 2015 (Fox, 2015). Any UK BAP status is taken from the UK Biodiversity Action Plan (UK BAP) (2007 review).

UK BAP Status
Occurrence Change
1976-2014 (%)
Abundance Change
1976-2014 (%)
Occurrence Change
2005-2014 (%)
Abundance Change
2005-2014 (%)
Not Listed
Decrease -30Large Decrease -54Decrease -15Decrease -10

Adults emerge from the last week of June, through July and into August, with adults still being found into September. There is a peak at the end of July and early August, or later in Scotland. There is one brood each year.

The Purple Hairstreak is one of the delights of summer, seen in oak woodland across the south of England, and more locally in other areas. It is particularly active in bright sunshine and, in the right woodland in early evening, this species can be seen in large numbers flitting around the tree canopy, and from tree to tree. Groups of several individuals chasing one another are not an uncommon sight. The butterfly primarily feeds on honeydew, but will occasionally feed from nectar sources such as Bramble.

Adults feed primarily on Honeydew (N/A). brambles (Rubus spp.), buckthorns (Frangula alnus and Rhamnus cathartica), Hemp-agrimony (Eupatorium cannabinum) and thistles (Carduus spp. and Cirsium spp.) are also used.

Eggs are laid singly (or less commonly, in groups of 2 or more), usually at the base of a plump oak bud, or cluster of buds, but can also be found on an adjoining twig and at various heights. They are laid on branches that are sheltered and that receive full sunshine - such branches are therefore on the southern side of the tree. There also appears to be a preference for solitary trees, such as those found at the edges of woods, or those that form part of a hedgerow.

Eggs are also most-often found on relatively mature trees (since these have the plumpest buds) on branches that are twisted and gnarled. Eggs are relatively easy to find in suitable locations during the winter months before the oak buds burst.

The eggs are bun-shaped but, on closer examination, more closely resemble a sea urchin. Each egg is white when first laid but can become discoloured when exposed to the elements, giving the appearance of being dark grey. The larva is fully-developed within the egg after around 3 weeks, but does not emerge until the following spring.

"Eggs laid on July 30th, 1900, and on the following seven days began hatching on April 8th, 1901, remaining eight months in the egg state. The egg is large in comparison to the butterfly, being 0.80 mm. wide and 0.50 mm. high. It is of a compressed spherical form, flattened at the base; the micropyle is sunken and finely pitted; the whole surface is beautifully reticulated of a more prominent structure than that of the "Blues"; it is composed of projecting points placed close together round the micropyle. On rounding the crown the pattern becomes more open and the points longer, on nearing the base they gradually diminish in size; all the points are connected by a fine network of elevated keels, but the whole pattern is irregular; the ground surface of the egg is finely granular, of a silvery or bluish-grey colour; the reticulations are pure white, resembling opaque frosted glass. To the naked eye the egg appears pearly white. When first laid and for many days it is of a slightly bluish tinge, gradually becoming white during the autumn; it remains unchanged through the winter and until hatching at the beginning of April." - Frohawk (1924)

The larva eats part of its eggshell on hatching before burrowing into a developing bud where it feeds fully-concealed. After the first moult, the larva lives outside the bud, under a loosely-spun silk web. This web catches all sorts of debris and acts as camouflage as a result. The larva is extremely well-camouflaged and, in later stages when the larva lies under an oak bud, is very difficult to locate. Some have suggested that the best method to find larvae is by feel, rather than sight! The larva rests during the day, feeding only at night and there are 3 moults in total.

The primary larval foodplants are Pedunculate Oak (Quercus robur), Sessile Oak (Quercus petraea) and Turkey Oak (Quercus cerris). Evergreen Oak (Quercus ilex) is also used.

1st Instar

"The little larva eats a circular hole in the crown of the egg, the micropyle being the starting point, and the time occupied in eating its way out is about twenty-four hours. Directly after emergence it is 1.5 mm. long and almost uniformly cylindrical, only being slightly attenuated posteriorly. The head is almost as wide as the body and cleft at the base of the crown in the shape of a heart. There is no medio-dorsal furrow down the body, and the sides are not flattened like the Lycaenidae larvae, but in structure and position of the hairs and in the general colouring there is a good deal of similarity between them. On both the first and last segments is a dorsal, shining, olive-brown disc, with a pair of pale olive-brown warts on the front edge of the anterior disc. Along the dorsal surface are two rows of hairs; each row is composed of three hairs on each segment, the first is very small, the second long, and the third about half as long; all three curve backwards and slightly to the side, so that the points of all six hairs of the two rows are diverging; on each segment is a sub-dorsal, shining, pale yellowish wart; between this and the spiracle are two hairs, the first is short and directed slightly downwards, the other backwards; there are four others below the spiracle, three being placed in a line and projecting laterally, and one lower down pointing downwards; the segments are strongly lobed laterally, in the centre of each lobe is a translucent shining wart, and immediately below is a spinous hair. All the hairs mentioned are serrated, with dark shining bases, and are dark brownish-black with light glassy tips; the claspers have each a couple of simple fine spines. The whole surface is densely sprinkled with minute black points. The ground colour is pale greenish-ochreous. The head is very shining olive-black, bearing a number of fine whitish hairs. The hairs on the first and last segments project over them. Owing to the late spring of 1901, the oak buds were only just starting to develop in size at the time of the hatching of the eggs on April 8th, therefore the author removed the outer husks and placed the young larva on the tender green embryonic leaves, which they readily fed upon. It is obvious from the manner in which the young larva search for an opening in the buds by burrowing into the loosened husks that it is usual for them to feed upon the buds as soon as they are sufficiently expanded for them to get at the more tender parts. Consequently in a state of nature the hatching of the eggs and the expansion of the buds undoubtedly coincide. Before first moult, and thirteen days old, it measures 2.5 mm. long. The colour is pale ochreous, with a medio-dorsal darker line and oblique lateral stripes. They burrow into the centre of the buds and often so deeply that only the anal segments are exposed." - Frohawk (1924)


2nd Instar

"The first moult took place on April 24th, 1901. Before the second moult, about twenty days old, it measures 4.20 mm. long. The ground colour is pale ochreous, a dark medio-dorsal line terminating in a dark spot on the anal segment; it is bordered on either side by a creamy-white line which runs off obliquely from the third segment to the first, where it encircles a pale, shining green disc situated in the centre of the anterior segment; along the sub-dorsal region is a series of oblique whitish stripes, one on each segment, bordered below by rufous and above by ochreous. The spiracular region is mottled with rust-brown on a pale primrose-yellow ground; the dilated lateral line is also primrose colour. The surface is sprinkled with white serrated hairs, each with a fine, shining brown, truncated base, keeled with fine black ribs, forming fluted pedestals, and the entire surface is covered with fine reticulations. The spiracles are of the same colour as the body and almost indistinguishable owing to the numerous lenticles scattered over the body." - Frohawk (1924)

3rd Instar

"The second moult occurred on April 30th. Before the third moult, about twenty-five days old, it measures 9.5 mm. long. The shape is now broad and compressed, resembling the form of a wood-louse larva. Except being rather richer in colour, it is similar in all respects to the previous stage. The dorsal disc on the first segment, which is rather sunken, is pale shining greenish-white, striped with olive and beset with numerous serrated olive-coloured hairs and lenticles; a smaller but similar disc is situated on the anal segment. The head is completely retractile, being hidden beneath the broad, rounded and flattened anterior segment while at rest, and protruded while crawling. It still feeds on the unexpanded buds, eating out the centre in the same manner as Cyaniris argiolus feeds on holly berries. The general colouring bears a great similarity to the ochreous-brown outer cases of the oak buds. When a larva was placed upon freshly expanded young oak leaves it refused to feed on them, so it was returned to the unexpanded bud, when it immediately began feeding on it as before." - Frohawk (1924)

4th Instar

"The third moult on May 7th. Eight days after the third and last moult, fully grown, it measures 15.9 mm. in length; it is very broad and flattened; the entire colouring is much more intensified than in the previous stage, the oblique markings are rich brown and the medio-dorsal stripe is dull black, the lightest sub-dorsal and lateral lines are primrose-yellow on the posterior segments, gradually becoming more ochreous on the middle segments; the anterior disc is a pale pearly colour, and that on the posterior segment is darker; the spiracles are brown. The whole surface is densely clothed with short, serrated ochreous spines, each on a pedestal base, similar to the previous stage. The head is sienna-brown, with a very polished surface on the lobes of the crown, and fringed with short whitish hairs in front; the clypeus is whitish; the legs are brown, the claspers and ventral surface light ochreous-yellow. The manner in which the larva is capable of concealing itself among the bracts is remarkable. It spins silk over the stems, bracts and bases of the leaves, and then eats its way into the centre of the expanded buds and young shoots so as to remain more or less hidden; the silk cords retain all the parts that would otherwise fall, which afford a covering for the larva. Even that portion of the larva that remains uncovered is so wonderfully similar in general appearance to the ochreous and brown bracts that the disguise is rendered perfect and must form a most admirable protection to the larva against its enemies. On May 17th the first larva ceased feeding and remained on a leaf at the base of the stem of oak; the following day it crawled restlessly about. The colour had then assumed a much duller appearance, having a lilac hue along the dorsal surface and below the oblique dusky marks a dull ochreous-olive hue prevailed. The writer then placed some earth and moss at the bottom of the receptacle in which the larva were kept, and the one ready for pupation soon disappeared amongst it (and others did likewise on becoming fully grown) and pupated on May 23rd. The larval stage occupies about forty-five days." - Frohawk (1924)

The pupa is generally formed in a loose cocoon just under the surface of soil, moss or leaf litter, or possibly in the crevice of a tree. It has also been found in ants' nests. This stage lasts around 4 weeks.

"The pupa measures 10.20 mm. long; it is stoutly proportioned; the thorax is rounded and swollen; the abdomen is also rounded and curves to the anal segment, which has no cremastral hooks; the ventral surface is rather flattened; the head is round; at the base of the wing is a very slight angular projection; excepting the wings, the surface is densely sprinkled with extremely short minute spines with radiating starred summits, and along the spiracular line they rise into moderately long spines, each bearing a number of extremely fine branching bristles, mostly on the apical half. The entire surface is very finely reticulated. The ground colour is a bright sienna or rust-red, becoming paler at the head, wings and limbs, all of which are streaked with dark purple-brown; the thorax and abdomen are speckled and blotched with the same dark colour; the largest blotches form sub-dorsal series; the spiracles are light amber. The ventral surface of the abdomen is bare of markings. The surface is rather glossy. The pupa is not attached to anything; it simply lies on its ventral surface, a slight network cocoon spun on the surface of the ground at the base of the moss or other growth." - Frohawk (1924)