Eugen Johan Christoph Esper (1742-1810) was a renowned German naturalist of the late 18th and early 19th centuries. Originally a student of theology, Esper eventually found his true calling in the study of natural history, which he undertook while working as a tutor for a wealthy family of the Bavarian landed gentry, earning his doctorate in that field at the University of Erlangen in 1781. He wrote on a variety of subjects including mineralogy, geology, corals, sea sponges, the Linnean system of classification system—at that time still considered a revolutionary new approach to making sense of world's biological diversity—and butterflies. Inspired by Linnean rigor in classification, Esper undertook an ambitious work: a comprehensive account of all the known butterflies of the world. The first product of this effort, an illustrated inventory of Europe's butterlies, became Esper's most celebrated publication and over a century later would eventually find a place in the Nabokov family library.

Butterflies in systematic perspective

First issued as a series of folios between the years 1776 and 1807, Die Schmetterlinge in Abbildungen Nach Der Natur Mit Beschreibungen: Europäische Gattungen was eventually formally published as a set of five volumes. Interleaved throughout were magnificently colored plates featuring intricate illustrations of butterflies, often in the various stages of their life cycle, and notably combining depictions of both the upper and lower surfaces of a butterfly’s wings in a single illustration. In the care Esper took to reference identifications of a given species by other leading naturalists of the day—Carl Linnaeus and Johann Fabricius among them—and in the compact, detail-packed nature of his illustrations, this important work marked a shift in the European study of natural history and the publishing industry promoting it. Fascinated as young Nabokov was with their gorgeous illustrations, between the covers of these thick volumes he would also have seen the groundwork being laid for the systematic study and classification of the world's animal life that was to follow over the coming centuries.

Collector, curator, and professor

For his monumental butterfly inventory, Esper drew from his own extensive butterfly collection and those of other 18th century collectors. He also had developed an extensive and much-admired collection of corals from around the world. As Nabokov eventually would in his own time, Esper served as a curator of his university's natural history collections, and, again like Nabokov, the personal collections he amassed over a lifetime of research would eventually become prized features in the holdings of institutions that would preserve them for future generations, including the Bavarian State Collection for Zoology in Munich, home to Germany's largest collection of butterflies and moths.

Though separated by over a century, Nabokov and Esper's life histories would share one more commonality: Both became professors known to enthrall their students. In his years at the University of Erlangen, so the record tells us, it was not uncommon for Eugen Esper's lectures to close to the sound of loud applause from his audience in a packed lecture hall.