The spring weather has baffled Britain's butterflies, with some emerging unusually early due to the warm March and others hit by the April deluge, conservationists said.
Some spring species emerged several weeks early in March, but the wettest April on record and the continuing rain this month has delayed the appearance of many butterflies.
And wildlife charity Butterfly Conservation is warning that if the wet conditions continue it could affect the breeding success of some species later in the year.
Cold, wet weather makes butterflies less active, reducing feeding and mating.
Among those to put in an early appearance were the small blue butterfly, which was seen on March 30 on the Isle of Wight, one of the earliest dates recorded for the species and several weeks ahead of its usual emergence between mid-April and early May.
The wood white, which usually emerges in late April or May, was seen on April 10 in Surrey, while the threatened pearl-bordered fritillary was also recorded earlier than usual, Butterfly Conservation said.
But as the wet weather took hold, butterflies started to be spotted later than normal, with the common blue and brown argus appearing in early May, rather than being seen in mid-April which they would be in warm years.
Marsh fritillaries and Adonis blues both emerged in the final week of April in 2011 but were not seen until the second week of May this year.
Richard Fox, Butterfly Conservation surveys manager, said: "Overall, butterflies have experienced an unusual spring so far - the mild winter and very warm March led to some extremely early emergences, but the cold, wet April delayed the emergence of other species.
"The worry about this April is that the butterflies that did emerge will have poor breeding success due to the bad weather.
"Unless conditions improve in the next few weeks their opportunities to breed will be very limited and, therefore, we may see population crashes later in the year or next spring."
He added: "Last year we had a hot spring and a poor summer. This year we're having a poor spring, so let's hope the summer is better."