UK Butterflies

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Large Tortoiseshell

Nymphalis polychloros

nim-FAY-liss po-lee-KLAW-ross

Wingspan
♂ 68 - 72 mm, ♀ 72 - 75 mm

Checklist Number
59.029

Large Tortoiseshell

Nymphalis polychloros

nim-FAY-liss po-lee-KLAW-ross

Wingspan
♂ 68 - 72 mm, ♀ 72 - 75 mm

Checklist Number
59.029


In Victorian times the Large Tortoiseshell was considered widespread and common in woodland in southern England. However, this beautiful insect has since suffered a severe decline and there have been less than 150 records since 1951. This butterfly, whose numbers were always known to fluctuate, is generally considered to be extinct in the British Isles, with any sightings considered to be migrants from the continent or accidental or deliberate releases of captive-bred stock. Several causes of its decline have been suggested - including climate change, parasitism, and the effect of Dutch Elm disease on one of its primary foodplants. The hope, of course, is that this butterfly is able to once again colonise our islands. Although previously found in many parts of England, Wales and Scotland, the greatest concentrations were in the midlands, south and east of England. This species has not been recorded from Ireland. Recent sightings have come from the south coast, in particular from South Devon, South Hampshire, the Isle of Wight and West Sussex.

This species was first defined in Linnaeus (1758) as shown here (type locality: Sweden).

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 found primarily in woodland, especially those containing sallows whose flowers provide a primary nectar source for the adults in the spring.

This species is believed to be extinct as a resident, although sightings are reported in most years which are assumed to be immigrants. As such, no conservation action is relevant.

Adults emerge in July and August and overwinter in this stage, re-emerging in the spring. There is one brood each year.

This butterfly hibernates shortly after emerging from the pupa, finding a hibernation site in log piles or outbuildings. On emerging from hibernation in the spring, the butterfly feeds from Sallow flowers and sap runs and the adults mate soon after emerging. This powerful-flyer is often difficult to see when not feeding, as it can be difficult to approach, taking off at high speed at the least disturbance.

Description to be completed.

Eggs are laid in a cluster around a terminal twig of the foodplant, usually 3 metres or more above the ground and on the sunny side of the tree. They are yellow when first laid, but turn brown just before hatching. Eggs hatch in about 3 weeks.

"On April 6th, 1912, the Hon. N. Charles Rothschild captured at Symond's Yat two female polychlorus, which he very kindly sent direct to the author. These were received on the 8th, and upon their arrival they were at once fed with sugar and water, which they continued drinking a long time, and were then placed on branches of elm. One died on April 23rd without depositing. Upon dissection she proved to be full of eggs, apparently ready for extrusion, as they were of a clear yellow-ochre colour, of the same hue as when first laid. The other female deposited a large batch of eggs, numbering 212, between 1.30 a.m. and 1 p.m. on April 14th. Another female, also captured on April 6th, in the Forest of Dean, was likewise received on the 8th, and fed on sugar and water every other day during captivity. Although fine, sunny weather prevailed she did not deposit until April 20th, when she laid a batch of 120 eggs upon a slender branch of sallow, between 1 and 2.30 p.m. These began hatching on May 7th, and by noon the following day all were hatched, remaining eighteen days in the egg state. Those laid on April 14th hatched on May 6th, being twenty-two days in the egg stage. The egg is 0.80 mm. high and dome-shaped. The micropyle is flattened and very finely reticulated. There are from seven to nine longitudinal keels, which rise on the crown, where they are much elevated, but rapidly decrease in height on traversing the side and form only a slight ridge over the basal half; they are fluted and resemble white, frosted glass frills. They are only white on the upper half. The usual number is eight, occasionally only seven, and sometimes nine. The spaces between the keels are delicately ribbed transversely, each space having about forty ribs. When first laid the colour is a pure yellow-ochre, which changes to apricot-yellow when twenty-four hours old. Then it very gradually assumes a slightly duller colour by the third day, and by the fifth day it is dull ochreous-buff; and by gradual degrees the colour increases in depth to amber-brown when a week old. The white keels give the entire batch a drab appearance to the naked eye. Under microscopic power the ground colour is amber, checkered with subcutaneous chestnut-red markings caused by the maturing of the larva. After remaining for a few days the basal half assumes a more ochreous hue, while the apical half turns duller, and finally the ground colour becomes pale ochreous, the dark hairs of the larva showing through the shell, and the black head covers the greater part of the crown. This, combined with the white keels, gives the eggs a dull purplish appearance. The eggs are usually laid on the terminal branches near the top of an elm; often the tallest trees are selected for the purpose. They are deposited in a cluster, closely packed, with their sides glued together with the glutinous substance which attaches them to the branch. If a thin twig is chosen the eggs encircle it in a band, but if a branch about 5 mm. in diameter is to receive the eggs they only partly surround the stem. During deposition the female remains clinging to the branch with closed wings until the whole batch is laid. Both in colour and shape the egg of polychlorus closely resembles that of E. antiopa, both being of a yellow hue when first laid and later assuming an amber ground colour, which in all other British Vanessidae is green. The keels of the upper portion of the egg of polychlorus are deeper than those of antiopa, the former being more like those of atalanta. They are also deposited in a similar manner to antiopa." - Frohawk (1924)

The larvae are gregarious in all of their instars, living in a communal web, although they disperse prior to pupation. When disturbed the entire group will jerk in unison, which is clearly designed to deter predators. Early collectors often obtained this species by collecting the conspicuous larval webs and rearing the offspring through. This stage lasts around a month.

The primary larval foodplant is elms (Ulmus spp.). Aspen (Populus tremula), poplars (Populus spp.), sallows (Salix spp.) and willows (Salix spp.) are also used.

1st Instar

"The larva makes its exit by eating away the crown of the egg. Upon emergence the whole brood crawls to a young leaf and spins a web over the surface as it goes, and all the members congregate together on the leaf and soon start feeding. Directly after emergence the larva is very small, measuring only 2.12 mm. long. It has a comparatively large head, which is black and shining, with a few scattered fine black hairs. The segments are clearly defined and slightly wrinkled transversely; each segment has ten very long, curved, finely serrated black hairs with grey tips and bulbous bases, each rising from a rather large dome-shaped tubercle. There are five on each side. Those above the spiracle (one dorsal, one sub-dorsal and one super-spiracular) are very long and curve forwards; immediately behind the spiracle is the fourth, which curves laterally and downwards; the fifth is below the spiracle and also projects downwards. On the base of the claspers are two fine, simple hairs. The surface is densely covered with minute black points, excepting the tubercles, which are smooth. The spiracles are black, as are also the feet of the claspers. The legs are large and terminate with an amber-coloured claw. The colouring of the body, including the legs and claspers, is a light olive-yellow, inclining to citrine. When five days old it measures 4.8 mm. in length. The ground colour is then ochreous-yellow, checkered and speckled with brown, chiefly forming medio-dorsal and lateral series of longitudinal markings. On the anal segment is a blackish disc. They cover the leaves and twigs upon which they live with web." - Frohawk (1924)

2nd Instar

"The first moult occurred on May 9th, 1911, remaining in the first stage nine days. After the first moult, twelve days old, it measures 8 mm. long. The ground colour is ochreous or pale amber-yellow, checkered and speckled with dull black; the ventral surface and claspers are whitish; the bases of the long hairs of the previous stage are now developed into ochreous-coloured tubercles, each with a number of whitish hairs rising from the base, terminating in a much longer and stouter one, which is also whitish and finely serrated; numerous other fine black and whitish hairs of various lengths are sprinkled over the body, each having a black bulbous base. The spiracles are black, surrounded with dull white. The head is shining black, beset with fine black, serrated hairs. The surface of the body is still densely covered with minute black points, as in the first stage. They remain gregarious in habit, and during the process of moulting they all collect in a dense mass; occasionally, when thus gathered together resting, they all at the same time start violently jerking their bodies from side to side at the rate of about every two seconds." - Frohawk (1924)

3rd Instar

"The second moult May 13th, 1911, being only four days in the second stage. After the second moult it measures 21 mm. long; the body is slender, cylindrical and of uniform thickness; it is almost similar to the previous stage, excepting that all the tubercles (spines) are much longer and more thickly beset with hairs. The medio-dorsal black line is broken up by the medio-dorsal series of amber tubercles, all the markings are distinct and form a checkered pattern of black, amber and pearl-white, chiefly running in longitudinal rows, the dorsal series being amber and the sub-dorsal black and white; the lateral stripe is yellow and the ventral surface smoky. The head is black and shining, notched on the crown and beset with fine white hairs , the legs are also black. The last two segments are dusky with a black dorsal disc, the largest is on the anal segment; the claspers of the anal pair are also black, the remaining four pairs are ochreous. They still remain gregarious." - Frohawk (1924)

4th Instar

"The third moult occurred on May 18th, 1911 , the third stage occupying five days. After the third moult and shortly before fourth, and twenty-four days old, it measures 25.4 mm. long. It is very similar to the former stage, excepting all the markings are more distinct and the pale amber tubercles with their side spines all terminate in sharply pointed black spinelets; the head and body are sprinkled over with delicate white hairs. They are still gregarious and collect in a mass to undergo the moulting process." - Frohawk (1924)

5th Instar

"The fourth moult took place on May 26th, 1911, being eight days in the fourth stage. After the fourth and last moult, thirty days old, fully grown, it measures 41.3 mm. long. The head is bilobed, with a deep notch on the crown, black and studded with various sized black warts and tubercles, each bearing a whitish hair; those on the lobes of the crown are developed into spine-like tubercles. The body is almost cylindrical, of uniform thickness, excepting the first segment, which is disproportionately small. The segments are transversely wrinkled posteriorly. The spines are long, branched and sharply pointed, capable of penetrating the fingers; all are amber-coloured, each spine terminates in a sharp black spinelet. The spines run in longitudinal rows; the medio-dorsal series extends from the fourth to eleventh segments inclusive; the first segment is spineless, the second, third and last segments each have four spines, the remaining segments have seven each; these are arranged as follows: medio-dorsal, sub-dorsal, super and sub-spiracular. Those of the medio-dorsal series have a single branch directed forwards; the spines also bear numerous pale hairs. Altogether there are sixty-eight spines. The ground colour is velvety black, excepting the anterior sub-dorsal area of each segment; the surface is sprinkled with white warts, each emitting a fine white hair; these give the dorsal surface a grey effect, and the spotless black area has a blue-grey velvety bloom next to the segmental divisions, adding to the blue-grey appearance. The fine black medio-dorsal line is bordered with amber and each spine is seated on an amber band, the other paler amber-yellow markings checker the spiracular region; the spiracles are black surrounded by pale amber; the ventral surface is checkered purplish-grey; the claspers are ochreous and legs black, the hind claspers are black; the last two segments have each a black, rounded dorsal disc, the larger one being on the anal segment. The larval state occupies about thirty days. They remain gregarious until fully grown, when they start wandering about in search of a suitable site for pupation, which in a natural state appears to be any adaptable place for suspension." - Frohawk (1924)


The pupa is suspended head-down, attached by the cremaster to a twig or other platform. This stage lasts around 2 weeks.

"The pupa; are found under ledges of palings near trees upon which the larvae have lived. The author has seen the fully grown larva: voluntarily fall from the topmost branches of a lofty elm standing by a high road, over which they were crawling in various directions. The pupa averages 25.4 mm. in length. Lateral view: The head is beaked in front and rises to an angulated keeled thoracic point, the sunken meta-thorax forms a deep concavity with the first abdominal segment. The abdomen is swollen on the third and fourth segments, it then curves and tapers to the anal segment, which terminates in a long, slightly curved cremaster, deeply grooved both dorsally and laterally, and furnished with an ample terminal cluster of black hooks; the cremaster is striped black and pearly-white. The abdominal series of sub-dorsal points are strongly developed on the middle segments, and the medio-dorsal series are very small and black; the ventral outline is slightly undulating, otherwise forming a fairly straight line. Dorsal view: The head has two sharply pointed, ear-like projections, and three other lateral points on the wing, first at the base, second on the basal inner margin, the third on the anal angle; between these points the outline is concave; the abdomen tapers to the extremity. The colour is variable, varying from coppery-ochreous to dull smoky-bronze more or less checkered with dull pink and black in the dark form, to golden-bronze variegated with rust-red, pinkish and greenish-olive in the light form. The dorsal points have the tips orange and black. Most specimens have brilliant silver-gilt patches of colour surrounding the dorsal points on the meta-thorax and first two abdominal segments; but the metallic spots vary greatly in size, often are altogether absent, in others just visible, while in many they are large and glittering. It is suspended by the cremastral hooks to a pad of silk." - Frohawk (1924)