By way of example, this Skipper was initially mis-identified as a Small Skipper due to a russet brown marking on the end of its antenna and a seeming absence of the twirly hooked end tips.
However a closer inspection after boosting contrast and saturation in the image revealed the very faint presence of the arc of pale checks characteristic of a Large Skipper and a darkened forewing-tip.
It appears that the hooked antennae tips were curling outwards and backwards so from this perspective both were concealed from the camera.
The moral of the story being of course that its always worth getting as many images as you can from as many angles as you can, starting far back at a distance that you know will not disturb the butterfly and moving slowly avoiding sudden jerky movements that will cause the butterfly to skip away. Even if its small in the frame you can always zoom in for ID purposes and discard the image once an ID has been made.
Non Visual Characteristics Can also Eliminate a Suspect
Distribution
Both the Small Skipper and Essex Skipper have expanded their ranges northwards. However, the Essex Skipper is still the more south-easterly of the two species, being seen as far north as the Humber and west to the Severn Estuary. The Small Skipper, like the Large Skipper can be seen even in Wales and Cornwall and as far north as Northumberland recently.
Flight Times
The Large Skipper is the early bird of the three, flying from late May, peaking in mid July and ending in late August. The Small appears next, flying from early June until early September. The Essex Skipper has the narrowest flight period, being seen on the wing from the end of June until the end of August. Bear in mind that flight times can vary significantly by region typically being later further north and also seasonally as butterflies may sometimes take advantage of favourable spring and early summer conditions or respond to adverse conditionas by emerging earlier or later.
Host Plants
All three species are single brooded and feed on various grasses such as Yorkshire-fog (Small Skipper), Creeping Soft-grass (Essex and Small Skippers) and Cock's foot (Large Skipper). Early stage larvae overwinter in the sheaths of long grasses and winter cutting and "tidying" can negatively affect populations. For more information visit www.butterfly-conservation.org
Resources
My own records and observations in Oxfordshire and Norfolk
Butterfly Conservation Society - Species Information and Factsheets:
R Lewington - Pocket Guide to the Butterflies of Great Britain and Ireland
All images taken by and © Kiri Stuart-Clarke. All rights reserved