 |
 |
 |
|
|
Small Tortoiseshell
Behaviour and Ecology The daily behaviour of males, mentioned briefly above, centres around the need to nectar during the morning and to find a mate. To do this, males will set up a temporary territory which they will defend for an hour or so. If no female has entered the territory within that time, the male will move on and try his luck elsewhere. Both sexes spend the night deep within patches of nettles and are late risers (typically on the wing from 10am). Once fertilised, the female will spend the rest of her life searching for suitable sites at which eggs can be deposited. The females lay their eggs during the afternoon, selecting patches of young nettles in sheltered but sunny locations. Both common and small nettle are used as a food plant by the caterpillars but the females reject most clumps as being too small, too sheltered or not young enough. An ideal nettle bed is one that occupies a large part of a sunny border and which has been cut in early June to promote tender regrowth – not exactly the sort of thing tolerated by many gardeners. Because the eggs are laid in groups, the caterpillars are initially gregarious, living within an untidy web. When they are nearly fully-grown, they will disperse and live singly, still on nettle. This stage may last for about four weeks from egg to pupa. If you encounter a Small Tortoiseshell fluttering about in your centrally-heated house in the later part of the year, then ‘rescue’ it to an outbuilding or shed (and not outside) where the temperature will remain more stable and help secure a successful hibernation. Identification This species should be recognisable to most observers, with both sexes similar in appearance. An unusual colour form (known as semi-ichnusoides) may be encountered occasionally. This forms results when an individual is exposed to high temperatures during the chrysalis stage; it’s appearance shows reduced amounts of orange and the dark spots smudged together producing a less strongly marked and blurred effect. The camouflaged underwings are useful in concealing individuals that have begun hibernation. The caterpillars range in colour from black to variegated yellow, with spiky growths emerging at intervals along the back. Even though this colouration deters most predators, a good number of caterpillars are lost to parasitic wasps and flies.
The use of gardens - results from Garden BirdWatch In southern Britain there are two broods each year (not obvious from the Garden BirdWatch reporting rate for 2003, while further north in Scotland there is typically just the one. Adults from the second brood are seemingly uninterested in mating. Instead they prepare for hibernation from August and they may be encountered either in outbuildings or indoors in houses. It is such overwintering individuals that make up the Garden BirdWatch reports from the months of November through into February.
The Garden BirdWatch reporting rates show that this is a commonly encountered butterfly in gardens, perhaps more so in rural gardens than suburban and urban ones.
Small Tortoiseshells can be encountered right across Britain and Ireland but are at their most common in the south and east. They occur on the Channel Isles, the Isle of Man, the Hebrides, Orkney and even Shetland. Click here to see a map showing the distribution of Wall Browns within gardens at the national level, as recorded by BTO/CJ Garden BirdWatchers during 2003.
Click here to see what the region codes on the above graph mean. |
|
|
|
Garden
BirdWatch | BTO
Home | CJ
WildBird Foods Home |