In 2013, the best summer weather for seven years led to a resurgence in butterfly numbers. The insects had been hit especially hard by gloomy, exceptionally wet weather in 2012.

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Results of the Wider Countryside Butterfly Survey, published this week, reveal that farmland species of butterfly, including the Brimstone, Common Blue, Small Copper, Small Skipper, Large Skipper and Small Tortoiseshell all bounced back in 2013 after experiencing a crash in numbers during 2012.

Although winter and spring were unsettled in 2013, the summer was one of the hottest, and sunniest, since records began in the UK.

Last year recorders saw an average of 85 butterflies of 5 species per-survey, in monitoring over July and August – almost double the numbers recorded in 2012. The Small Tortoiseshell, which has suffered an ongoing decline, recorded its best summer since the start of WCBS; the species appears to have almost doubled its range between 2012 and 2013.

Common blues also flourished, with a five-fold increase noted compared to 2012. Cabbage white numbers doubled on the year. However, the Holly Blue and Red Admiral were worse-off, suffering declines compared to 2012.

WCBS, conducted by Butterfly Conservation, the British Trust for Ornithology (BTO) and The Centre for Ecology & Hydrology (CEH), has run annually since 2009. It counts butterflies in more than 850 randomly selected 1km-squares across England, Wales, Scotland and Northern Ireland to assess the health of butterfly populations across the wider countryside rather than at specially managed hotspots such as nature reserves.

Butterfly Conservation said the creatures are a good indicator of the health of an ecosystem, as they respond rapidly to changes in environment and land management, as well as playing key roles as pollinators and prey for birds and other wildlife. The conservation group said that, as 70 percent of the UK's land is in agricultural use, it is essential to monitor butterflies in these areas, to gauge the health of the countryside with greater accuracy.

However, figures from Defra published last year show that butterfly numbers have almost halved since 1990.  

The survey's researchers said hedgerows and field margins have been shown to be especially important for sustaining butterfly numbers, and said habitats such as these have played a vital part in the recovery seen between 2012 and 2013.