The disappearance of the wall brown (Lasiommata megera) from areas of southern England has mystified conservationists for two decades.
It was believed that the loss of unimproved grassland was significant but new evidence has suggested that the butterfly is dying out because its caterpillars are pupating in the warmer autumns caused by climate change, instead of overwintering and hatching in the following spring.
There are two broods per year, flying from late April to mid-June and again from July to September. The eggs are laid singly on the blades of various grasses such as cock’s-foot and Yorkshire-fog, hatching after ten days. Caterpillars of the first brood pupate after five weeks, emerging as adults after a further two weeks. The second brood caterpillars are supposed to overwinter, remaining in this stage for about six months, pupating the following year.
If they hatch in a warm September or October, these autumn butterflies are a lost generation, leaving no caterpillars that can survive to become butterflies the following spring.
Below is Ian Bushell’s photograph of the Lasiommata megera seen during last week’s Butterfly Transect.
Its identity was confirmed by Mike Fuller, County Recorder:
Many thanks for these results of the survey and also the picture.
Yes, the Wall is of interest as several others have been reported in localities from where they haven’t been seen before. They are obviously having a good second generation and moving about during warm spells of weather. The one in your picture is a male. They are rarely seen in double-figure numbers except on some favoured downland sites. It’s possible that it will be a strong contender for Butterfly of the Year.
Good to hear from you and I hope you are able to continue with the butterfly survey at Southwick and I’ll always be pleased to hear of your results.
Section 41 species of principal importance under the NERC Act in England.
UK BAP status: Priority Species
Header photo by Charles J Sharp [CC BY-SA 4.0]