Worcestershire Record No. 3 November 1997 p. 8


Mike Williams

At a time when many of our butterfly species are in decline, it is encouraging to be able to report one species which is currently expanding its range and for the first time ever (if we leave aside a possibly dubious record from Arley at the turn of the century) has been reported from Worcestershire. The butterfly in question is the Essex Skipper Thymelicus lineola which is almost identical in appearance to the familiar Small Skipper Thymelicus sylvestris which occurs throughout the county in areas of tall grassland. The Essex Skipper is found in similar habitats but flies on average a week to ten days later, typically emerging around the middle of July, although there is considerable overlap in the two species' flight seasons. Historically, the Essex Skipper has been confined to south-east England but over recent years has expanded rapidly to the north and west possibly taking advantage of grasses, typically cock's foot Dactylis glomerata or creeping soft grass Holcus mollis on which it lays its eggs, along the verges of our growing road network. The butterfly was completely unknown from the Midlands counties until 1992 when the species was reported from an old railway line in the east of Warwickshire. Since then it has spread westwards and by the end of 1996 had been reported from 27 tetrads within the county. At the same time, the Essex Skipper has been advancing on Worcestershire from the south with a first report from Gloucestershire in 1996. By the end of that summer it had been reported from 18 tetrads and had already been seen as far north as Cheltenham.

Its imminent arrival in Worcestershire was, therefore, eagerly anticipated and sure enough the butterfly obliged with a report of two individuals on 20th July this year. Perhaps more surprising, however, was the manner and whereabouts of its discovery with the first record coming via two visiting Butterfly Conservation members from Suffolk, where Essex Skippers are widespread, at Monkwood NR. Unfortunately, the significance of this find was not realised and the record only came to light this September amongst a long list of other sightings submitted to the West Midlands branch organiser. What is so intriguing is that, whether colonisation has occurred from the south or the east, if the Essex Skipper has reached Monkwood then it must surely be present elsewhere in the county but we shall now have to wait until 1998 to find out.

Separating out Essex from Small Skippers as adults is not easy but by no means impossible. The main distinguishing feature of the Essex Skipper is that the tips of its antennae are completely black on both the upper and underneath sides. The Small Skipper also has some black on the upper surfaces but the underside of the antenna tip is a fulvous brown. This feature is actually more noticeable than it sounds, if one can get the butterfly to stay still long enough! The Essex Skipper looks as if it has dipped its antennae into a pot of black paint. Another distinguishing feature to look out for 'Is the underside tip of the forewing which in the Small Skipper is distinctively olive buff in contrast to the rest of the wing, while with the Essex the whole underside of the wing is uniformly orange.

Prospective Essex girls (and boys) should try looking at these differences in a butterfly field guide over the winter so that by next July they will be able to help in efforts to find out exactly how much of Worcestershire is now part of the expanding Essex empire.

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