Leaf beetles of the genus Chrysolina are among the largest and most conspicuous members of the Chrysomelidae, the third most diverse beetle family both in Switzerland and worldwide. Yet despite their size, the Swiss representatives of one particularly tricky species group, the subgenus Stichoptera, have long been shrouded in confusion. A new review published in Alpine Entomology has now untangled the mess, confirming four species and one additional subspecies in the Swiss fauna, excluding one dubious record, and delivering a stark conservation warning: Chrysolina sanguinolenta, once locally common across the country, has not been recorded for fifty years and must be feared extinct.
The study, led by Christoph Germann and colleagues, combined a critical re-reading of nineteenth and twentieth century literature with the examination of old museum specimens and recent field material from national institutions such as the Natural History Museum Geneva, the Natural History Museum Basel and the Natural History Museum Bern, alongside numerous private collections. The central European members of Stichoptera form a notoriously difficult species complex. Species bearing a red margin on the elytra were repeatedly confused or misinterpreted, and the nineteenth century literature even treated Chrysolina marginalis Duftschmid, 1825 and Ch. sanguinolenta (Linnaeus, 1758) as separate species, although they are now considered synonyms and both names likely referred to a mixture of species.
The first thorough revision of these morphologically similar beetles was provided by Helliesen in 1912, based on a study of type material including that of Ch. sanguinolenta held at the Linnaean Society in London. His identification key, used together with illustrations of the male genitalia, remains usable today. A more recent key by Winkelman and Debreuil (2008) also proved useful. Kippenberg (2020) then revised the predominantly alpine Ch. latecincta and its subspecies, synonymising the Swiss-endemic Ch. latecincta vallesiaca with the nominate subspecies and recording Ch. latecincta norica from Switzerland for the first time.
The impetus for the new Swiss review came in October 2020, when Chrysolina kuesteri, a species only confirmed for the Swiss fauna in 2012, was observed in surprisingly high abundance near Sion in Valais by Annette Geiser-Barkhausen and Urs Lemmenmeier. Germann revisited the locality and collected adults and larvae, and the team also analysed pitfall trap samples from vineyards around Salgesch and Varen. In total, 86 voucher specimens of Ch. kuesteri were examined. Only 21 were collected before 2000, spread over a range of 120 years, but 65 have been collected since 2000, suggesting the species has markedly increased in abundance during the last two decades.
The rearing experiments delivered some of the study’s most striking biological insights. Six couples of Ch. kuesteri from Mont d’Orge near Sion were kept in small plastic boxes and fed on the garden plant Linaria purpurea. Oviposition was observed from November until January, the first larvae appeared in early February 2021, and the larvae passed through five moults between mid-February and mid-April. The first pale yellowish pupa was found on 30 April, buried in quartz sand at the bottom of the boxes, and the first adult hatched on 29 May. Remarkably, some of the adults from autumn 2020 were still alive at that time. In the field, fifth instar larvae were found near Sion on 22 March 2021, feeding on Veronica hederifolia, a host plant record that matches an earlier observation by Peter Sprick in Lower Saxony, Germany.
Larvae of the alpine Ch. latecincta latecincta were also reared, from adults collected at Griespass in Valais at around 2400 metres altitude. Fifteen adults were kept alive in couples on Linaria purpurea. Eggs were laid from mid-September 2021, and one larva survived to moult twice before entering a quiescent phase from mid-December to February, during which it neither fed nor moved. It died in early March of unknown reasons. Three females then laid more than 20 eggs in mid to late March 2022, and the resulting larvae hatched in early April, moulting repeatedly through May and likely a fifth time by early June, when the first pupa appeared. This developmental schedule suggests that at high altitudes, where thick snow cover persists until early summer and slows plant growth, a larval development from spring to summer is likely the rule.
The review also settled the status of Chrysolina gypsophilae in Switzerland. Blanc et al. (2012) had recorded this species from Geneva, but the new examination traced the record to three female specimens from the collection of Charles Maerky, a collection with a reputation for frequent labelling errors. The specimens supposedly came from montane localities such as Le Grammont, Chandolin and Kippel in Valais, which seems odd for a species otherwise known from lowland areas. Because of this unreliability and the absence of any other material in collections, the authors consider the occurrence of Ch. gypsophilae in Switzerland dubious and advise against adding it to faunistic lists unless new data become available.
Ch. kuesteri is now confirmed to be locally common around Sion and Leuk in central Valais, with several previously unknown populations discovered between late 2020 and 2021. Most beetles were observed within vineyards, with smaller numbers on south-facing rocky steppe sites. Valais is a particularly well sampled area for Coleoptera, yet most collections made during recent decades did not contain the species, and the authors speculate that a warming climate or changes in insecticide use in vineyards may have contributed to the apparent increase. Similar observations of rising numbers have been made in the Kaiserstuhl area of southwest Germany. Ch. rossia, restricted to Ticino in Switzerland, appears stable, with a fair number of recent observations, and its recognisability even on photographs makes citizen science data usually trustworthy.
The picture for the alpine taxa is more mixed. Ch. latecincta latecincta is a high-altitude species potentially threatened by anthropogenic climate change in the long term, although no drastic population decline was apparent from the data. Ch. latecincta norica seems to have similar habits but with more widely scattered populations. A remarkable isolated locality is Passo Campolungo near Fusio in Ticino, separated from the nearest known populations by some 70 kilometres and several mountain ranges. Seven specimens collected before 1927 by G.C. Champion are held in the Natural History Museum London, and four more from 1912 to 1936 are in the Fontana collection in Lugano. A targeted field trip in September 2021 confirmed the presence of the host plant Linaria alpina but yielded no beetles, and the authors warn that this interesting isolated population may already have gone extinct in the 87 years since its last sighting. Intensive searches at Bergalga in Avers in 2012 and 2017 also failed to find the species.
The fate of Ch. sanguinolenta is the study’s most alarming finding. Arguably the most widespread species of the subgenus, found across the Palaearctic from Great Britain to eastern Siberia, it was once locally common in Switzerland, with records from Geneva, Vaud, Valais and Graubünden. The most recent Swiss records date back to the early 1970s, when Carlo Poluzzi found the species in abundance at Begnins in Vaud and even reared it on Linaria vulgaris, documenting his results in a drawing now kept in Geneva alongside his collection. His observations revealed pale brownish larvae, in contrast to the dark brown or black larvae of Ch. kuesteri and Ch. latecincta. Given the amount of collecting activity in many former localities in recent decades, the sudden decline cannot be attributed to a lack of sampling, and a September 2022 search in the vineyards around Begnins proved unsuccessful. The authors note that historical confusion with Ch. kuesteri and other relatives obscured the species’ true decline, and they urgently call for targeted surveys to find surviving populations and for a better understanding of the causes of its disappearance. From a conservation standpoint, current knowledge remains too poor to evaluate the Swiss Stichoptera taxa using IUCN criteria, but the review provides the foundation for future assessments, and the authors caution biological recorders and conservationists working on similarly complicated taxa against uncritically downloading data from online databases, including museum collections, unless the records have been recently verified by a specialist.
Subject of Research: Entomology
Article Title: A review of the Chrysolina species – subgenus Stichoptera Motschulsky, 1860 – in Switzerland, with notes on distribution, conservation and preimaginal stages ( Coleoptera , Chrysomelidae )
Article References: Germann, C., Geiser, M., & Borer, M. (2023). A review of the Chrysolina species – subgenus Stichoptera Motschulsky, 1860 – in Switzerland, with notes on distribution, conservation and preimaginal stages (Coleoptera, Chrysomelidae). Alpine Entomology, 7, 69-82. https://doi.org/10.3897/alpento.7.105937
Image Credits: AI Generated
Keywords: Chrysolina, Stichoptera, leaf beetles, Chrysomelidae, Switzerland, Alpine Entomology, conservation, larval biology, review, species, subgenus, Motschulsky
News Source: Margaret Porter. (October 18, 2026). Swiss leaf beetle review reveals one species extinct and another thriving. Scienmag.
