Wednesday, April 08, 2015

Small Tortoiseshell

Not the greatest picture but I was very excited to see the first butterfly in the garden this year. It's a small tortoiseshell, Aglais urticae. It is one of our commonest butterflies in the British Isles and, in the south at least, has two broods per year. The second brood emerges in September - October and hibernates over winter to emerge in the first warm days of spring. Unlike many species these are not colonial breeders; rather they range about and lay eggs whenever favourable habitat is encountered. They sometimes travel considerable distances, regularly crossing the English Channel. 
They are creatures of habit: the males get up around 10am (when it's nice weather), fly around for a couple of hours feeding and enjoying the sun, then after lunch they find a suitable territory in a sheltered sunny south-facing spot near nettles and fly up to check out any other small tortoiseshells flying past. If male, they have a 'fly-off' which involves spiralling up just behind and above the opponent before diving down and repeating. The winner stays put, but if after about an hour and a half he's had no luck with the ladies he finds another territory and hangs out until around tea time when he calls it a day. 
Should a lady pass she is pursued at great speed, sometimes for up to three hours, before getting down and dirty in the nettle-patch. The lady then spends the rest of her time selecting with great care the ideal nettle leaf to lay eggs on. They lay 60 - 100 eggs at a time, usually underneath the topmost leaf on an edge of a nettle patch in full sun. 
The Large Tortoiseshell used to be widespread in the wooded areas of southern Britain but mysteriously declined and became extinct around 40 years ago. 
I must just put in a pitch for the book from which the above information was gleaned: The Butterflies of Britain and Ireland by Jeremy Thomas and Richard Lewington. The former is Professor of Ecology at Oxford; the latter is surely one of the best wildlife illustrators around today. The illustrations in this book are exquisite and the text is distilled deep knowledge about these creatures. It's published by British Wildlife Publishing who do the British Wildlife magazine and several other field guides which are highly recommended.
So we're more than a quarter of the way through the year and approaching the hundredth post. To be honest it hasn't been that difficult finding species and I suspect it will be difficult deciding which to leave out as spring progresses, but I do find myself wondering which new species I'll be able to find next January, February and March.
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