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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 the most-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 the Orkneys and Shetlands.
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.
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.
The primary larval foodplants are Common Nettle (Urtica dioica) and Small Nettle (Urtica urens).
Adults feed primarily on Betony (Stachys officinalis), Bramble (Rubus fruticosus agg.), Carline Thistle (Carlina vulgaris), Dandelion (Taraxacum agg.), Devil's-bit Scabious (Succisa pratensis), Field Scabious (Knautia arvensis), Greater Stitchwort (Stellaria holostea), Hawkweeds (Hieracium/Hypochoeris), Heather (Calluna vulgaris / Erica spp.), Hemp Agrimony (Eupatorium cannabinum), Ivy (Hedera helix), Knapweeds (Centaurea spp.), Marjoram (Origanum vulgare), Primrose (Primula vulgaris), Privet (Ligustrum vulgare), Ragwort (Senecio jacobaea), Thistles (Cirsium spp. and Carduus spp.), Thyme (Thymus polytrichus) and Water Mint (Mentha aquatica).
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.
This species displays considerable variation in both the upperside ground colour and the familiar upperside pattern and markings. Much work has been carried out in this species to discover how temperature shock in the late larval/ early pupal stage can affect the development of pigments in the imago. These experiments have assisted our understanding of how and when the pigments are 'mapped' in the Vanessid butterflies. The Small Tortoiseshell appears to be particularly sensitive to temperature shock, and this species has been widely bred in the past in the hope of producing extreme environmentally controlled aberrations such as ab. semi-ichnusoides. Extreme shocks of either heat or cold during the last 24 hours of the larval stage and the first 48 hours of the pupal stage can disrupt the natural process of metamorphosis and inhibit the normal processes in which organic chemicals create the colouration of the wing scales. The expression of aberration through temperature shock is a graduated process; one level of exposure creates ab. semi-ichnusoides, a little more fuses all three black blotches along the costa of the forewing to create ab. conjuncta, and the most extreme exposure produces an almost entirely melanic form known as ab. osborni. The conditions required to produce the latter forms are thought to be so extreme that they lie right on the very cusp of extremes of temperature that would be fatal to the larva or pupa. Consequently these forms are rare in captivity and extremely unlikely to be met with in the wild. It is difficult to ascertain how frequently any of these aberration occur in the wild, however it is a rare event that exposes the newly formed pupa or transitional larva to the necessary conditions for metamorphosis to be disrupted in this way, and this is supported by the paucity of historical sightings of the extreme aberrations in the wild. That is not to say that the lesser of the aberrations do not occur however, and an ab. semi-ichnusoides presents a particularly striking sight when nectaring on a garden buddleia amongst typical individuals. It has been speculated that severe late frosts could possibly cause instances of these aberrant forms, as well as a larva/pupa being exposed to particularly strong sunlight after having the normally sheltered pupation site disturbed in some manner. Environmental influences are not the sole cause of aberration in this species however, and there are many genetic aberrations which the observer could encounter at any time. Occasionally the orange ground colour is replaced entirely by a pale whitish buff (ab. lutea), as well as various transitional shades leading to this. Similarly, sometimes the orange colour is replaced by a brownish-purple hue and this is known as ab. brunneoviolacea. There are in excess of 105 named aberrations known to occur in Britain and a selection is described below.
ab. alba (Cosmovici) The normal costal yellow patches replaced by white. (Easily confused with faded post hibernation specimens in which the yellow pigment has bleached with age. This aberration does not have the 'washed out' appearance of faded markings). ab. bellieri (Cabeau, 1923) Upperside with white ground colour. ab. caerulapicata (Raynor) A delicate chalky blue suffusion to the apex of the forewings. ab. conjuncta (Neuberg) On the forewings the three black costal spots are united into one long bar. The twin discal spots are absent, the marginal black band narrow with small blue spots. Hindwings very dark showing a discal series of pale brown spots some distance from the margin. Margin black, narrow, and with a full row of blue spots. ab. embryonalis (Solowjev) Upperside ground colour pale yellow-fulvous with marked reduction in all black markings. ab. erythrophaea (Fritsch) Yellow costal patches and the yellow patch on the outer edge of the black spot of the inner margin are warm scarlet-brown. ab. falcoides (Rouss) The wings narrow and the angles so exaggerated that the butterfly resembles the Comma in general shape. ab. latericolor (Raynor) Upperside ground colour brick red. ab. nigrita (Fickert) On the forewings the two upper black costal spots are united to form a single black blotch. The twin discal spots are absent. Hindwings entirely black with no marginal lunules.
ab. osborni (Donekier) All three black costal spots united to form a single black bar. No white apical patch. Black margin very wide covering the twin discoidal spots and uniting with the black spot on the inner margin. Marginal lunules yellow brown. Hindwings a uniform dark brown, lighter towards the anal angle and with no marginal spots. ab. pallida (Mosley) Upperside ground colour light ochre-yellow. ab. semiichnusoides (Pronin) On the forewings the two upper black costal spots are united to form a single black blotch. The twin discal spots are absent, and there are no blue marginal lunules on the forewings. Hindwings with the black extended to the margin, covering the usual transverse fulvous band. The margins have normal blue lunules.
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 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 4 moults in total.
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.
Large TortoiseshellDescription 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.
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.
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 has been derived from the author's own observations and the information contained in the following works:
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![Small Tortoiseshell - imago - Quarndon, Derby - Apr-04 [Mark Nowak]](phpBB/gallery/images/upload/ba7be32be838571604e4a1d07a4060a8.jpg "Small Tortoiseshell - imago - Quarndon, Derby - Apr-04 [Mark Nowak]")
![Small Tortoiseshell - imago - Bridport - 07-Jun-09 [Jules Cross]](phpBB/gallery/images/upload/c1ebed4a56136c91e5dd196ad36eff6a.jpg "Small Tortoiseshell - imago - Bridport - 07-Jun-09 [Jules Cross]")
![Small Tortoiseshell - ovum - Unknown location - Uknown date [Reg Fry]](phpBB/gallery/images/upload/f34d0eb5bf819e5e5cafce874db093fb.jpg "Small Tortoiseshell - ovum - Unknown location - Uknown date [Reg Fry]")
![Small Tortoiseshell - larva - Ashford Hill NNR - Uknown date [Tim Norriss]](phpBB/gallery/images/upload/02032b2ec930f64975849ae6fdbe1722.jpg "Small Tortoiseshell - larva - Ashford Hill NNR - Uknown date [Tim Norriss]")
![Small Tortoiseshell - pupa - Unknown location - 30-May-05 [REARED] [Matt Berry]](phpBB/gallery/images/upload/674168203a55f02d12b56a3fad84bf79.jpg "Small Tortoiseshell - pupa - Unknown location - 30-May-05 [REARED] [Matt Berry]")
