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Red Admirals
small scale immigration of Red Admiral and some Small Tortoiseshell did bring a bit of colour to some gardens in early September. At the time of writing, it is unclear whether we will have a mild extended autumn – or an early winter to close this disappointing butterfly season. What is evident, is that 2012 has been a set-back, and we should not expect a prompt return to “normal” .
Other Species. The Purple Emperor was late emerging at Theberton this year, and was not reported from any other sites. The Marbled White was again flying in Landseer Park.
Other Conservation Activity. Suffolk Branch of Butterfly Conservation has made representations in the planning process for the Anglia ONE Windfarm, in which we drew attention to the need for mitigation of the destruction of habitat for the Wall Brown colony breeding astride the proposed landfall site just north of Bawdsey. The proposed route inland passes clear of the Silver-studded Blue colony at Martlesham Heath, so that is no longer a concern. An important project to improve the condition of 14 fragmented heathland sites in the Ipswich area has been funded with a grant from WREN. This was the subject of a separate briefing by the project officer.
Illustrations by Douglas Hammersley.
Small Copper
Red Admirals - Large and Small
The influx of Red Admirals in autumn led a number of people to comment on a perceived wide variation in size.
Obviously, there is a natural spread of size, but I would have said that it is less (as a percentage) for Red Admirals than for many other species. The good book (Emmet & Heath 1990, The Butterflies of Great Britain and Ireland, MOGBI Vol 7) gives the typical wingspans as: male 64 - 72 mm (12% spread) female 70 - 78 mm (11% spread)
This means the normal range of 8mm for either sex amounts to a 11-12% variation, which does not sound dramatic. On the other hand, the maximum wingspan difference between a small male and a large female is 14mm, or 21%. Bear in mind though, that this leaves a much larger impression when judged by wing area, as 78 squared divided by 64 squared amounts to an extra 48% of wing area - so an observer naturally sees this as much larger. (OK, I know their wings are not really square!)
Another factor is dwarfism. When food plants dry out, undernourished larvae sometimes pupate one whole instar (skin cast) early, and are undersize when they emerge as adults, maybe 15 to 25% smaller than typical. I doubt there were dwarfs in the early September immigration though. Interestingly, my own 2012 season began with a very early sighting of a tiny Orangetip, and as an isolated specimen, this stood out as a dwarf.
