, Oxfordshire Heslop's attitude to butterfly collecting has been described by Oates as "turning the gentle pursuit of butterflies into an extreme country sport". He collected his first example of
Leptidea sinapis (wood white) on the tracks at a railway station, only narrowly escaping being hit by an oncoming express train. In 1968, aged sixty-four, he waded and swam into a flooded
Woodwalton Fen to collect examples of
Lycaena dispar batavus (large copper). He had a particular interest in
Maculinea arion (large blue); in 1949, he rediscovered the existence of the species in the
Polden Hills of Somerset, and later discovered previously unknown populations of it in the
Quantock Hills and near
Minack Head in
Cornwall. In his obituary of Heslop, the naturalist John F. Burton wrote that he had probably been the greatest living authority on the distribution of the species. During his time in Nigeria, he specialised in collecting butterflies of the genus
Charaxes. Heslop's greatest obsession, however, was with
Apatura iris (purple emperor), which he called in his diary "the monarch of all the butterflies". He made the suggestion that its genus name, of uncertain origin, was connected to the Ancient Greek verb , meaning "I deceive". He captured his first specimen of
Apatura iris at Fox Hill, near
Petworth in West Sussex, in July 1935, having narrowly failed to catch three during an expedition with De Worms and a Colonel Labouchere at Bignor in 1933. De Worms considered Heslop's acquisition of specimens from sixty-five species to be the most ever attained by a single person, and described Heslop as "probably the foremost authority of his day" on the history of British butterflies. Among butterfly collectors, he acquired the nickname "the Purple Emperor" after
Apatura iris, following a tradition of ascribing to collectors the name of a particular species: de Worms, for instance, was nicknamed "the
setaceous Hebrew character" after the moth
Xestia c-nigrum. Heslop kept thorough notes on where and how he acquired his butterflies, but refused to share detailed information about where he found rare species such as
Apatura iris, for fear that other collectors would damage the sites or butterfly populations. Michael Salmon, a historian of British butterfly collecting, describes Heslop as a "[naturalist] with the blood of the old Aurelians in [his] veins", referring to the eighteenth-century pioneers of the discipline who formed London's
Society of Aurelians. Oates calls him "one of the last great collectors of British butterflies, and certainly the greatest of the purple emperor". On Heslop's death, his wife Eileen donated his collection of British and African butterflies to the
Bristol City Museum. The collection included over 150 specimens of
Apatura iris alone.
Notes and Views of the Purple Emperor Heslop published
Notes and Views, originally intended as a guide to collecting
Apatura iris, in 1964, alongside the naturalists George E. Hyde and Roy E. Stockley. It comprises a collection of thirty-three papers, often reprints from academic journals, of which twenty-nine were written by Heslop, three by Stockley and one by Hyde, who also provided the book's colour photographs. Heslop funded part of the publication himself, gathering the remaining funds by private subscription. Oates has described the book as "gloriously anachronistic", partly because most of the papers had been written during the early-to-mid 1950s and were already behind Heslop's own knowledge of
Apatura iris, and partly owing to the archaic, classicising style of Heslop's writing: Oates judges that there is "more Latin and Greek in the book than science". Reviewing the work in ''
The Entomologist's Record and Journal of Variation'', the journal's editor S. N. A. Jacobs wrote that it had "more appeal to the enthusiastic amateur than to the professional entomologist" and criticised Heslop's vagueness as to the precise locations of
Apatura iris habitats, but praised the detail of the work and Hyde's photography. Oates considers it "a masterpiece in obsession, a meditation on an all-pervading passion, and a literary monument to the history of butterfly collecting". == Later life ==