Peter Hättenschwiler, Leading Bagworm Moth Specialist, Dies at 93

Peter Hättenschwiler, one of the world’s foremost specialists on bagworm moths, died on 17 August 2021 in Uster, Switzerland, at the age of 93. Born in St. Gallen on 26 September 1927, he devoted five decades of his life to the study of the moth family Psychidae, known in German as Sackträger, or sack-carriers. His passing marks the loss of an entomologist whose meticulous taxonomy, generous mentorship and encyclopaedic knowledge shaped bagworm research across Europe and far beyond.

Bagworm moths are among the most unusual families of Lepidoptera. Their caterpillars construct portable cases, or sacks, from silk and incorporated fragments of plant material, sand or other particles, and many species are notable for wingless, even legless females that never leave their cases. This peculiar biology makes the family notoriously difficult to study: females are rarely seen, males are short-lived, and species identification often depends on the architecture of the larval sacks as much as on adult morphology. Hättenschwiler mastered all of these approaches, combining classical genital dissection with careful observation of sack construction, a dual competence reflected in the identification keys he produced for both genera and sacks.

His professional career lay outside entomology. After school, he began an apprenticeship as a precision mechanic at the former Zellweger AG in Uster, the town with which he remained associated for his entire life. He worked on the development of machines for testing yarns, especially silk, and on the establishment of quality standards that remain relevant today as the Uster Statistics. Rising to become the company’s chief technology officer, he travelled widely as a customer consultant, visiting many countries and seizing every opportunity to collect bagworm moths on his journeys. His travels eventually took him to the USA, China and New Zealand, among other destinations, and his fieldwork on several continents enriched his taxonomic revisions with material few European specialists could access.

The origin of his lifelong passion for Psychidae is closely tied to his decades-long friendship with Professor Willi Sauter, who received his doctorate in 1956 at ETH Zurich with a thesis on the morphology and systematics of the Swiss species of the genus Solenobia, now Dahlica, under Professor Jakob Seiler. Sauter was later regarded as one of the best European psychid experts, and it was he who encouraged and supported Hättenschwiler in 1977 to describe his first three new taxa, based on knowledge the two had gained together. Many more descriptions followed, and one species, Dahlica sauteri, was dedicated to his friend. Their collaboration culminated in the series of papers on the system of the Palaearctic Psychidae published in Nota Lepidopterologica in 1991, 1999 and 2004, which remain of tremendous importance for bagworm research, providing a species list, keys to the genera and keys to the sacks of the Palaearctic fauna.

Over a publishing career spanning 50 years, Hättenschwiler produced more than 50 papers dealing exclusively with the Psychidae, 20 of them in Nota Lepidopterologica. He introduced the family group names Placodominae, together with Sauter in 1991, and Scoriodytinae in 1989, and described 31 taxa in total, ranging from the Alps to the West Himalaya, the Peloponnese, Tunisia, the Altai, southern Spain, China, Iran, the Caribbean, the Maldives and Papua New Guinea. His faunistic treatment of the Psychidae in the Swiss volume Schmetterlinge und ihre Lebensräume, published in 1997, stands as a model of profound research on the family, equipped with aids for species determination and excellent photographs. His 1989 revision of the New Zealand genus Scoriodyta established a new subfamily and described numerous new species and forms.

His taxonomic breadth defied any single focus. Because of his enormous notoriety as a leading bagworm specialist, entomologists worldwide turned to him with their questions, resulting in a very broad spectrum of publication themes, with descriptive taxonomy accounting for the largest proportion. He described a parthenogenetic bagworm from China, Acanthopsyche muralis, and provided an overview of the known parthenogenetic species of the family. He documented new bagworms from oil palm plantations in Papua New Guinea, published on the biology of Psychidae larvae and the details of their sacks, and investigated questions as varied as the size variation of adults within a species and the defensive behaviour of psychid caterpillars. His type specimens and other material are deposited in numerous museums and private collections.

Hättenschwiler was equally renowned for his warmth and generosity. Colleagues recall packages from him as small works of art, with accurately placed stamps, and small jars filled with a special mix of alcohol and formalin containing the wingless females of the Psychidae, individually wrapped in pink tissue paper and packed in absorbent cotton. He freely shared literature, precisely pinned specimens and expertise without reservation, and acknowledgements in countless publications testify to the support he gave to other lepidopterists. One colleague, meeting him in 1974 as a young entomologist after publishing a first small essay on bagworm moths, was bound to the psychids by Hättenschwiler’s extensive experience, knowledge and generously exchanged specimens, and has remained faithful to the family ever since.

His empathy extended beyond science. One of his mentors, the well-known Austrian psychid expert Leo Sieder, gave his large psychid collection to the Karlsruhe Natural History Museum in the 1960s for health reasons, then fell into a deep psychological crisis because he missed his work with his beloved bagworms. Hättenschwiler convinced the old man to start collecting again, and the result was several more boxes of valuable material and a marked improvement in Sieder’s health over the years. Similarly, after the death of a colleague’s son in 2000, Hättenschwiler persuaded the grieving entomologist to resume his activities, accompanied by an extensive package of literature and Psychidae. He was, by all accounts, a devoted family man, married to his wife Ruth for 65 years, with three children, seven grandchildren and two great-grandchildren, whose annual Christmas summaries, written jointly with Ruth, were eagerly awaited by friends.

His institutional contributions were substantial. He was the soul of the Entomological Society of Zurich, its president from 1968 to 1974 and an honorary member from 1979. He joined the Societas Entomologica Europaea as an ordinary member in 1977 and became an honorary member in 2007. He maintained close contact with all important Psychidae specialists worldwide, including Wolfgang Dierl in Munich, Jean Bourgogne in Paris, Leo Sieder in Klagenfurt, Donald R. Davis in Washington, Gaden Robinson in London and Toyohei Saigusa in Japan, as well as specialists of other Lepidoptera families such as Chunsheng Wu in China, Ole Karsholt in Copenhagen and Erik van Nieukerken in Leiden.

After his move to the Tertianum Residenz Brunnehof in Uster in 2017, Hättenschwiler transferred his entire collection of about 40,000 specimens, mainly Psychidae, together with associated archival materials, to the Entomological Collection of ETH Zurich, ensuring that his life’s work remains accessible to future generations of researchers. With his passing, lepidopterology has lost an outstanding specialist, and all who knew him will miss his friendly manner, his helpfulness and his competent professional advice. His legacy endures in the taxonomy of the bagworm moths, in the identification tools he left behind, and in the many scientists he inspired and supported throughout his long career.

Subject of Research: Obituary: Peter Hättenschwiler, bagworm moth specialist

Article Title: In Memoriam: Peter Hättenschwiler 26.09.1927–17.08.2021

Article References: Sobczyk, T., Arnscheid, W., & Greeff, M. (2021). In Memoriam: Peter Hättenschwiler 26.09.1927–17.08.2021. Nota Lepidopterologica, 44, 249-256. https://doi.org/10.3897/nl.44.76454

Image Credits: AI Generated

DOI: 10.3897/nl.44.76454

Keywords: entomology, lepidoptera, Psychidae, bagworm moths, taxonomy, obituary, Switzerland, Nota Lepidopterologica, Memoriam, Peter, ttenschwiler, scientific research