I am sorry to disappoint your reader David Mooney, but his butterfly photograph (Is this the Duke, June 17) is not of the rare Duke of Burgundy, which Butterfly Conservation is trying to conserve in Yorkshire. It is another species called the Speckled Wood.

All the same, Mr Mooney is lucky to have this one in his conservatory. Only a few years ago it was a Yorkshire rarity itself. It has profited from global warming and moved north. The Speckled Wood first appeared in our York garden in 2005, and now we see it every year.

The Duke of Burgundy, by contrast, has been a Yorkshire resident pretty well since records began, but in declining numbers. It is a national rarity, with a few scattered colonies in the Wolds. Apart from a handful of sites near Morecambe Bay, this is its only home in northern England.

Its carefully protected downland colonies are not far from Mr Mooney’s home in Bridlington, but he is not likely to see it. I have seen just one in many years of butterfly watching, and that was in the Cotswolds.

Peter Hollindale, Grange Garth, York.

• YOUR recent photograph of what is thought to be a Duke of Burgundy fritillary, seen by David Mooney of Bridlington in his conservatory, appears to be a Speckled Wood butterfly, a species that has increased in great numbers in recent years, spreading north because of global warming. It is frequently seen in gardens and meadows throughout spring and summer, over wintering in pupae and another generation in summer.

Your recent reporting of the Duke of Burgundy fritillary butterfly being lured to the Dalby Forest area should hold interest with all butterfly buffs.

This expansive area of woodland shelters many glades and butterfly rides allowing primrose and cowslip to flourish, the food plant of the larvae of the Duke of Burgundy fritillary. Let’s hope this rare butterfly becomes a success story.

Douglas A Heald, Huntington Road, York.