Butterfly populations in the United Kingdom have plunged to a 25-year low, threatening many species with extinction, according to the latest annual survey by the U.K. Butterfly Monitoring Scheme, a partnership between the Center for Ecology and Hydrology, Butterfly Conservation and the Joint Nature Conservation Committee.

Two wet summers in a row, combined with habitat loss due to agriculture and construction, have put the hurt on at least 12 U.K. butterfly species. Butterflies can't fly during heavy rains, so stormy weather interferes with their ability to breed, lay eggs and find food, according to a Butterfly Conservation statement.

Britain had its wettest summer in 100 years in 2007, according to The Daily Mail. 2008 was another wet one.

British butterflies had already been on the decline, but this new drop puts them at their lowest numbers in the 33 years since the annual monitoring scheme began.

Species particularly at risk include:

•    the High Brown Fritillary (Argynnis adippe)—the species has disappeared from 94 percent of its historic range, and now exists in fewer than 50 small colonies
•    the wood white (Leptidea sinapis)—down to under 100 colonies
•    the small tortoiseshell (Aglais urticae)—populations down 61 percent in the past 30 years
•    the Pearl-bordered Fritillary (Boloria euphrosyne)—down by two thirds in the past 20 years

"We just hope that this year we don't have another dire summer and that butterfly numbers are able to recover," Tom Brereton, head of monitoring at Butterfly Conservation, said in a statement.

Data for the study was collected by 1,500 volunteers conducting weekly monitoring visits to 920 sites across the U.K. Sixty butterfly species are known to exist in the U.K.; this study collects data on 50 of them.

Image: High Brown Fritillary (Argynnis adippe) via Wikimedia Commons