Printed
Butterflies
Pocket Guide to the Butterflies of Great Britain & Ireland by Richard Lewington, 2nd edition (2015). The leader in the field. It uses colour illustrations not photos. A 14-page at-a-glance guide, a double-page spread for each species, with: life cycle stages, emergence dates, food-plants, distribution maps.
Butterflies of Britain and Ireland: A Field and Site Guide by Michael Easterbrook (A&C Black 2010)
Britain’s Butterflies: A Field Guide to the Butterflies of Great Britain and Ireland David Newland, Robert Still, Andy Swash, David Tomlinson Fourth Edition (Princeton WILDGuides 2020)
Butterflies of Britain & Ireland Bebbington & Lewington (FSC WildID fold-out guide 2019)
Moths
British and Irish Moths: A Photographic Guide Chris Manley 3rd edition (Bloomsbury Naturalist 2021)
The Moths & Butterflies of Great Britain & Ireland edited by John Heath (Harley/Brill). In eleven volumes, for the deeply committed Lepidopterists only.
Field Guide to the Moths of Great Britain & Ireland by Paul Waring & Martin Townsend (Bloomsbury 3rd edition 2017) – The essential field guide to the macro-moths.
Concise Guide to the Moths of Great Britain and Ireland by Martin Townsend and Paul Waring (Bloomsbury 2nd edition 2019) ring-bound – Abbreviated version of the field guide above.
Field Guide to the Micro-moths of Great Britain & Ireland by Paul Waring & Mark Parsons (Bloomsbury 2012) – The essential field guide to the micro-moths.
Britain’s Day-flying Moths by David Newland, Robert Still & Andy Swash (Princeton WILDGuides, 2013)
Day-flying Moths of Britain Lewington (FSC WildID Fold-out chart 2006)
Hawkmoths of the British Isles Bebbington & Lewington (FSC WildID Fold-out chart 2007)
Caterpillars
Field Guide to the Caterpillars of Great Britain & Ireland Barry Henwood, Phil Sterling & Richard Lewington (Bloomsbury 2020)
Caterpillars of the butterflies of Britain & Ireland (FSC WildID fold-out card 2019)
Websites
Moths at Linford Lakes NR | Milton Keynes Natural History Society (mknhs.org.uk)
Butterfly Conservation is a substantial membership voluntary organisation that oversees the collection, analysis and use of records of Moths and Butterflies and works to improve their conservation. Their website has a search system to assist you to identify species. https://butterfly-conservation.org/butterflies/identify-a-butterfly
Butterfly Conservation – How To Identify White Butterflies
Google Lens: Go to google.com and there is a camera icon at the right of the search bar. Click on this, and you can drag and drop any image and it will do its best to identify it – so can be used for any flora and fauna, vertebrates and invertebrates etc. (as well as buildings, landscapes – anything, in fact.) Worth a look, but treat identifications with caution!