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Butterflies of
Britain & Europe
Small Tortoiseshell
Aglais urticae
LINNAEUS, 1758
Family - NYMPHALIDAE
subfamily -
NYMPHALINAE
Tribe - NYMPHALINI
introduction
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habitats |
lifecycle |
adult behaviour
Text and images protected by Copyright © Adrian
Hoskins 2007-2008, ( unless stated otherwise ) and must not be reproduced or published in part
or in whole elsewhere in any form without written permission from
Adrian Hoskins. Breach of copyright will be pursued by litigation.
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Adrian Hoskins
Aglais
urticae, female, Somerset, England
Introduction
Aglais urticae, male nectaring at bramble blossom,
Stockbridge Down, Hampshire, England
Lifecycle
In April,
female Small Tortoiseshells are often seen flying around young nettle patches,
where they lay their greenish eggs in large
untidy heaps
of 80-100 on the underside of the leaves.
The butterflies choose nettles that grow in warm sheltered
situations, e.g. at the bottom of south-facing hillsides, along dykes and riverbanks,
near hedgerows, and along disused railway cuttings. The summer brood is less
fussy about the situation, and will lay on nettle patches in gardens, in
woodland glades and rides, and on exposed hilltops. The
butterflies of both broods always favour young nettles, and rarely oviposit on the tougher
leaves of old growth.
The eggs hatch after about 10 days. Immediately after hatching, the
caterpillars spin a communal silk web around the
terminal leaves of the nettles. They shelter within the web overnight, or in
inclement weather conditions, and feed avidly whenever the sun shines.
If disturbed the larvae
react in unison, wriggling and jerking, presumably as a defence against
parasitoid wasps or flies. Nevertheless
a high proportion of larvae turn out to be parasitised.
When young, they can easily be mistaken for the caterpillars of the Peacock, but
Small Tortoiseshell larvae are paler, and even when quite small it is usually
possible to discern pale lines running along their backs.
Aglais urticae, 2nd instar larvae on stinging
nettle, Dorset, England
As
they grow, they split up into smaller groups, and spin new webs
after each moult, but become solitary when they enter the final instar. By this
time they are a dull blackish colour, spiky, with 2
prominent yellow lines running along their backs. The older larvae can often be seen curled in a J-shaped
posture, resting on nettle leaves, and if disturbed will coil
into a tight circle and drop to the ground.
The
chrysalis is variable in colour, ranging from grey to olive-brown,
often with a coppery or pinkish metallic sheen. It can be found suspended by the
cremaster, on woody stems, fence posts, walls, or beneath nettle leaves.
The butterflies emerge at dawn, about 12 days after pupation.
In
normal seasons there are 2 generations of this species, but in Scotland and at
high altitudes in northern England there is just a single brood. In the south of
England, in exceptionally warm seasons there may be a partial 3rd brood,
emerging in October.
Adult behaviour
Over-wintered adults typically awaken in late March or early April, and remain on the wing until early May. They are usually seen as singletons, The post-hibernation adults nectar mainly at dandelion, daisies and sallow catkins.
In spring they often bask on bare ground, on low foliage, or on bushes. On hot days they settle on the soil with wings closed, at which time the sombre "tortoiseshell" pattern on the underside affords them excellent camouflage. When settled the abdomen is usually raised so that minimum contact is made with the hot substrate.
Males establish vantage points in the early afternoon, and await passing females. When a female approaches she is intercepted, and the courtship ritual begins with both sexes settling on the ground with wings spread. The male approaches the female from behind, walks onto her hindwings, and vigorously drums her wings with his antennae. The pair then fly a short distance and repeat the process. Any other males which attempt to interfere are briskly chased away by the resident male, who then returns to his female to continue wing-tapping.
This bonding process continues for several hours, until just before dusk, when the female accepts the male's advances. At this point she leads him to a sheltered and shady spot, typically beneath a bush or hedge, where copulation takes place. It is likely that the pair remain copulated until the following morning.
Aglais urticae, nectaring at knapweed, Martin Down, Hampshire, England
The summer brood, which emerges in June, has a wide range of food sources available, and can be seen nectaring at bramble, hawkbit, small scabious and thistles. The second generation, which is always more abundant than the first, emerges in August. In late summer Small Tortoiseshells often visit flowery areas in the countryside, congregating to nectar at hemp agrimony, ragwort and marjoram. They also often visit gardens, where they are attracted to sedum, buddleia and michaelmas daisies.
In southern Britain the butterflies fly until late August or early September, when they enter houses, sheds, churches and unheated farm buildings to hibernate. In the north, they tend to enter hibernation in early August, after just a few days on the wing. It is common for Small Tortoiseshells to hibernate communally - I have frequently found them indoors in groups of 3 or 4, and once found a group of 17 hibernating clustered together on a ceiling in a hotel in Tayside.
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