UK Butterflies

Building a Community of Responsible Butterfly Enthusiasts in Britain & Ireland

Small Tortoiseshell

Aglais urticae

ag-LAR-iss ur-TY-see

Wingspan
♂ 45 - 55 mm, ♀ 52 - 62 mm

Checklist Number
59.027

Small Tortoiseshell

Aglais urticae

ag-LAR-iss ur-TY-see

Wingspan
♂ 45 - 55 mm, ♀ 52 - 62 mm

Checklist Number
59.027


The Small Tortoiseshell is one of our most-familiar butterflies, appearing in gardens throughout the British Isles. Unfortunately, this butterfly has suffered a worrying decline, especially in the south, over the last few years. This butterfly has always fluctuated in numbers, but the cause of a recent decline is not yet known, although various theories have been proposed. One is the increasing presence of a particular parasitic fly, Sturmia bella, due to global warming - this species being common on the continent. The fly lays its eggs on leaves of the foodplant, close to where larvae are feeding. The tiny eggs are then eaten whole by the larvae and the grubs that emerge feed on the insides of their host, avoiding the vital organs. A fly grub eventually kills its host and emerges from either the fully-grown larva or pupa before itself pupating. Although the fly attacks related species, such as the Peacock and Red Admiral, it is believed that the lifecycle of the Small Tortoiseshell is better-synchronised with that of the fly and it is therefore more prone to parasitism. This is one of our most widespread butterflies, occurring throughout the British Isles, including Orkney and Shetland.

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 can turn up almost anywhere, from city centres to mountain tops. As such, it is one of our most successful butterflies. It is most-often seen, however, where nettles grow in abundance, such as field margins. This butterfly is often encountered while hibernating in an outbuilding, such as a garage, shed or barn, where they may be found in the company of other individuals. Other hibernation sites include hollow trees and wood piles.

Despite being a widespread and common species in certain areas, the declining fortunes of this butterfly, especially in the south, mean that this butterfly is 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 -15Large Decrease -73Increase +13Large Increase +146

The adult butterflies can be seen at any time of the year, even on the last days of December or first days of January if the temperature is high enough to wake them from hibernation. However, adults normally emerge from hibernation at the end of March and start of April. There are typically 2 broods each year, except in the north, where there is usually only a single brood. Whether single or double-brooded, the butterfly is a familiar sight in late summer as it takes nectar to build up essential fats in preparation for hibernation.

The two sexes are almost identical in appearance, with the distinctive yellow and orange uppersides providing a contrast with the drab undersides that provide the butterfly a good deal of camouflage when hibernating.

In the afternoon, males set up territories, usually close to a nettle patch, where they rest of the foodplant or ground with their wings open, waiting for a passing female. When a female enters the territory, a most curious courtship begins. The male approaches the female from behind and starts to "drum" his antennae on the hindwings of the female, making a feint sound that is audible to the human ear. The female may fly a little distance, with the male following, where the process repeats. This can go on for several hours with the couple spending a good amount of time basking together. Eventually, usually in early evening, the female will lead the male into vegetation, often a nettle patch, and crawl between stems with the male following, where they eventually mate. They remain coupled until the following morning.

Adults feed primarily on Betony (Betonica officinalis), brambles (Rubus spp.), Buddleja (Buddleja spp.), dandelions (Taraxacum spp.), Devil's-bit Scabious (Succisa pratensis), Field Scabious (Knautia arvensis), Greater Stitchwort (Stellaria holostea), hawkweeds (Hieracium spp.), heathers (Calluna and Erica spp.), Hemp-agrimony (Eupatorium cannabinum), Ivy (Hedera spp.), knapweeds (Centaurea spp.), Michaelmas-daisies (Aster spp.), Primrose (Primula vulgaris), ragworts (Jacobaea spp.), sallows (Salix spp.), sedums (Sedum spp.), thistles (Carduus spp. and Cirsium spp.), Water Mint (Mentha aquatica), Wild Marjoram (Origanum vulgare), Wild Privet (Ligustrum vulgare), Wild Privet (Ligustrum vulgare) and Wild Thyme (Thymus polytrichus).

The female is quite choosy about where she lays, which is not surprising since she lays her green eggs in large batches and needs to ensure that the location is just right for the developing larvae. Typical sites are nettle patches containing relatively-new growth, and that receive full sun. Eggs are laid on the underside of a nettle leaf, usually one near the top of the stem and at the edge of the nettle patch. The eggs are not laid in neat rows, but piled on top of one another. Egg batches can contain up to 80 eggs which take some time to lay - typically between 20 and 90 minutes. The egg stage lasts between 1 and 3 weeks, depending on the weather.

"On May 4th, 1890, the author found (at Benfleet, Essex) a large batch of eggs just deposited; the butterfly was hanging helpless on the leaf with outspread wings. The eggs were in a dense heap, piled up many deep; in one view of the external layer about 200 were visible; the entire batch contained about 1,000 eggs, apparently the full complement of this species; these eggs hatched on May 18th, remaining fourteen days in the egg state. On May 25th, 1907, the author watched a female depositing between and 1.30 p.m. (at Rayleigh, Essex), during sunshine; she hung with expanded wings on the first leaf below the apical cluster of young leaves and deposited on the under side of the leaf a small batch of eggs, closely packed together and heaped up, about eighty in the top layer. On May 14th, 1910, a female was observed depositing a small batch of eggs, about fifty; these were also in a heap on the under side of a terminal nettle leaf. They hatched on May 23rd, being only nine days in the egg state owing to the warm weather during a few days previous to hatching. Another batch of eggs was laid on June 1st, 1910, followed by a spell of very warm weather, with a shade temperature of 79 degrees Fahr. They hatched very early on June 9th, being only eight and a half days in the egg stage. The egg stage lasts about ten days in normal weather. The egg is of an oblong shape, but fullest near the base, which is rounded and smooth; there are nine prominent longitudinal keels; these are fluted, white and glassy, very elevated where they commence round the micropyle, and gradually diminish in height as they descend the side, and finally disappear on reaching the base; the spaces between the keels are strongly ribbed transversely. The micropyle is finely pitted. The colour is a clear green, which becomes changed on the eighth day to paler ochreous, zoned at the middle with translucent green; and on the ninth day the dark head of the larva begins to mature, and rapidly develops during very warm weather in a temperature between 76 degrees and 80 degrees Fahr." - Frohawk (1924)

On emerging from their eggs, the larvae build a communal web, usually at the top of the nettle, from which they emerge to bask and feed. As the larvae grow, they move to new plants, building new webs along the way. This leaves a trail of webs, decorated with shed larval skins and droppings, that show the passing of time, and allows the patient observer to trace the larvae all the way back to the plant where the eggs were laid. The first experience that some people have of a Small Tortoiseshell is seeing these webs as they extend over stretches of nettle, with the larvae resting communally and quite visibly on the surface of the web, or feeding from nearby leaves.

Larvae have several techniques to avoid predation. When disturbed, a group of larvae will often jerk their bodies from side to side in unison, which must be a formidable sight to any predator. The larvae will also regurgitate green fluid and will, if necessary, curl up in a ball and drop to the ground. Larvae feed by both day and night and there are 5 instars in total.

The primary larval foodplants are Common Nettle (Urtica dioica) and Small Nettle (Urtica urens).

1st Instar

"Shortly after emergence the larva is very small, measuring only 1.25 mm. long; the anterior end of the body is stoutest; the head is large, black and shining and sparsely beset with fine black hairs. The body is a translucent ochreous-green and has ten (five on each side) longitudinal series of small tubercles, each bearing a long, simple, fine black hair slightly curved forwards, three above the spiracle, one immediately behind it, and one below, also two more simple hairs on base of claspers and others on the ventral surface; the legs and spiracles are black. The whole surface is covered with minute dusky granulations. Soon after feeding they assume a greenish hue. Upon emerging they quickly commence feeding on the young terminal leaves, perforating them and spinning a web all over the portion which they live upon. They are gregarious. When all the terminal leaves are consumed, they move off in a body to the topmost leaves of a neighbouring plant. If a large brood they break up into separate companies, from three to five, as soon as hatched." - Frohawk (1924)

2nd Instar

"The first moult occurred on May 31st, 1910, the first stage lasting nine days. Before the second moult it measures 4.8 mm. long. The ground colour is a pale primrose-yellow, mottled with dark olive-brown, forming a checkered, broad sub-dorsal band, a speckled spiracular line and a broken-up medio-dorsal line. There are seven rows of short, blunt, dull olive-green tubercles, each terminating in a long, serrated black bristle and shorter ones springing round the base. The medio-dorsal row is composed of one on each segment, from the fourth to eleventh inclusive; the three other rows on each side are sub-dorsal, super-spiracular and sub-spiracular; numerous other black bristles, varying in size, are scattered over the whole surface. The entire body is densely covered with very minute black points. The head is shining black and bristle-bearing like the body. When undergoing the moult they remain in a mass within a web." - Frohawk (1924)

3rd Instar

"The second moult on June 5th, the second stage lasting only five days. Before third moult, sixteen days old, it measures 8.5 mm. long. In general structure and colouring it is almost similar to the previous stage, but all the tubercles are more highly developed and the colouring is darker, it being more densely mottled with blackish, and the medio-dorsal line more continuous; the black spiracles are surrounded by whitish, and placed on a blackish wavy band bordered on either side by a lemon-yellow line; the whitish hairs sprinkled over the body have pale bulbous bases, giving the body a speckled appearance. The habits are also similar, and when moulting they rest in a heap one above the other." - Frohawk (1924)

4th Instar

"The third moult took place early morning June 10th, the third stage occupying only between four and five days. Shortly before fourth moult, it is 19 mm. in length. It is similar to the previous stage excepting being darker, the tubercles more fully developed, and the lateral series and claspers olive-green. They still remain gregarious and are similar in habits. The fourth moult occurred on June 13th, the fourth stage lasting just over three days." - Frohawk (1924)

5th Instar

"After the fourth and last moult, fully grown, twenty-six days old, it measures 22.2 mm. long. The body tapers at both ends, mostly so anteriorly; the first segment is small; the head is shining black and notched on the crown, and covered with greenish tubercles, each emitting a black serrated bristle; they vary in length. On the body are seven longitudinal rows of branching tubercles, stout at the base and somewhat abruptly tapering, the apex and each branch terminating in a moderately long, sharply pointed, simple black spine. The tubercles are of varying depths of olive-green, the sub-dorsal series usually black, but all are shining; the medio-dorsal series commences on the fourth segment and ends on the eleventh segment; the super-and sub-spiracular rows are palest in colour; the second, third and anal segments have each four tubercles. The body is rather thickly speckled with white and yellow warts, each bearing a spinous hair, all varying greatly in length; the longest are white and very finely serrated, and encircle the posterior sub-divisions of the segments, and similar white hairs are on the ventral surface and on the base of each clasper. The larva vary much in colour, some being almost wholly black, while others are variegated with a preponderance of yellow; every gradation of colouring exists between the two extremes. The normal form has the ground colour black on the dorsal surface, and more or less olivaceous below the spiracular line, spreading over the ventral surface, checkered with pale yellow and wavy yellow super-and sub-spiracular markings, forming a checkered, chain-like, lateral band enclosing the spiracles, which are black outlined with pale yellow; the legs and hind pair of claspers are black, the remaining claspers are green. After the fourth moult the larva separate, and frequently fold up a nettle leaf by dragging the edges together by silk, and therein live and feed in solitude; others disperse over the plants. When fully fed they wander away in search of suitable places for pupation; frequently they suspend themselves on palings or under coping stones, or other suitable ledges, often a considerable distance. from their food plant. During very warm weather the larva hangs suspended during the period of pupation for only about fourteen or sixteen hours; the actual act of transforming from the larva to pupa occupies four and a half minutes. At the last stage of casting the larval skin the pupa contrives, by curving the apex of the abdomen, to reach the pad of silk with the hooks of the cremaster while still adhering to the shrivelled larval skin, but immediately the hooks. touch the silk the pupa most vigorously twists to and fro and becomes securely anchored, and the larval skin usually becomes detached and falls. Within one hour the pupa is fully developed in form; at first it is more or less. uniformly green." - Frohawk (1924)


The larvae disperse as they become fully grown, and eventually wander off to find a suitable pupation site. The pupa is formed head down, attached to a stem or leaf by the cremaster. The colour of the pupa is quite variable, often having a beautiful metallic sheen. This stage lasts between 2 and 4 weeks, depending on temperature.

"The pupa measures from 20 mm. to 22 mm. long; it is rather slender in proportion. Lateral view: The head is sharply pointed in front; thorax rising to a central triangular point; sunken at the meta-thorax and first abdominal segment; the abdomen then swelling and curving to the anal segment, which terminates in a well developed cremastral process, which is grooved above and below and furnished with a dense mass of hooks; the ventral surface forms a gentle waved outline. The tongue sheath all but reaches the fifth abdominal segment. Dorsal view: The head is strongly bilobed, having a pair of well developed lateral conical points; thorax sharply pointed at the base of the wing; the inner margin is somewhat keeled and angular; the middle of wing is slightly sunken, the abdomen tapering. On the dorsal surface are three rows of conical points representing the dorsal tubercles of the larva; the medio-dorsal row is composed of a series of very small points, one on each segment from the second to seventh inclusive; the sub-dorsal rows commence on the meso-thorax and extend to the eighth segment, on which they are barely discernible; the lateral rows are represented by minute points only. The colouring is very various, even in the same brood, all reared together and pupated side by side under precisely similar conditions. For instance, a brood which pupated within a large glass cylinder with gauze covering the top, containing nettles, produced different forms; most of them were of a very beautifully gilded form, while others were of the dull smoky-brown type, and others were intermediate between these two extremes. This brood was from one batch of eggs, laid by a wild female on May 14th, 1910. The gilded form has the ground colour of the abdomen only a flesh colour, the rest of the pupa being wholly washed with very beautiful gold, reflecting coppery and green lustre; the entire surface is very finely reticulated and speckled with buff, brown and black; the black is chiefly on the head and dorsal points. Some have the ground colour delicate lilac-pink, washed with metallic copper over the thorax and opalescent at the base of the first few dorsal points. The most dusky form has the ground colour much duller and all the dark markings heavier. A dusky-olive wavy band passes obliquely over the centre of the wing, and a blotch of the same colour spreads over the apex; also oblique markings run from the dorsal points across the abdomen, and a spiracular longitudinal band formed of oblique markings, which become broken up on each segment, gives the pupa a somewhat checkered pattern. The ventral edge of the cremaster is black, from which the spiracular band originates. There is also a medio-ventral longitudinal band; the dorsal points are black with orange tips. Shortly before emergence the gilded form becomes metallic bronze-green and gold. The first imago emerged on July 2nd, 1910." - Frohawk (1924)