Aglais urticae, (Linnaeus, 1758) common name “Small Tortoiseshell”
Wingspan: male 50mm female: 56mm
Family: Nymphalidae.
Flight season April till October.
Widespread throughout the British Isles and Europe.
Habitat: May be present in most habitats: Gardens, Parks, moist woodland edges, roadside edges, orchards, hedgerows and practically anywhere Urtica dioica (stinging nettle) is abundant for the caterpillar’s food. Adults feed on the nectar of many wild and domestic flowers.
“Aglais urticae” hibernate over-winter in many types of man-made structures: Including garages, out-buildings, sheds, lofts and even churches.
In early spring the adults emerge from hibernation, the males often feed and bask in the morning sun. Early in the afternoon, they start to claim territories near beds of stinging nettles; waiting for the visiting females. Mating of this species usually occurs among stinging nettles, so they are very seldom seen.
The female lays the eggs in large clusters from 60 up to 200 eggs, the caterpillars hatch in around 10 days’ time and spin a dense web over the plant’s growing tip. They then feed and reside on underside of the young stinging nettles leaves.
The parasitic fly, “Sturmia bella” is now increasing in numbers due to global warming and is now a major concern for the Small Tortoiseshell population. The fly grub also preys on Red Admiral and Peacock eggs, but is not such a threat to these species as it is to the Small Tortoiseshell existence. It is believed the lifecycle timing of the Small Tortoiseshell, is more suited to that of the parasitic flies’ lifecycle. Because of this, the other two species of butterfly larvae are not so susceptible to eating the parasitic flies’ eggs. The fly lays its tiny eggs close to where the butterfly larvae are feeding, these are then consumed whole. When the grubs hatch out inside the caterpillar they feed on the inside of their host, avoiding the main organs. The fly grub eventually kills its host and emerges from the fully-grown larva or pupa, before it pupates itself. This could be one of the reasons why the Tortoiseshell population has recently been declining in numbers throughout the British Isles.