Ctenolepisma longicaudatum Escherich (1905) Became a Common Pest in Europe: Case Studies from Czechia and the United Kingdom

Development and Reproduction of a Japanese Strain of Ctenolepisma calvum (Ritter, 1910) at Room Temperature

Ctenolepisma calvum (Ritter, 1910) (Zygentoma: Lepismatidae) is a primitive wingless insect that causes damage to paper, and it is regarded as a pest of collections in museums, archives, and libraries. This species was recently discovered in Japan for the first time and may have already spread over large areas of Japan, but, currently, no information is available on the biological characteristics of C. calvum in Japan. In this study, we observed the processes of development and reproduction of C. calvum found in Japan at room temperature. Oviposition was observed from April to November, with a peak in early June. The average egg period was 56.9 days at average temperatures above 24.0 °C, and was 72.4 days at average temperatures below 24.0 °C. The 1st, 2nd, and 3rd instars lasted 4.7 days, 13.2 days, and 26.1 days on average, respectively, at average temperatures above 22.0 °C. Average instar periods were 23-28 days in 4th-7th instars and tended to increase in later instars. Instar periods also increased when the average temperature was 22.0 °C or lower. In individual rearing, the longest-living individual lived for approximately two years, up to the 15th instar. The head width grew at an approximate ratio of 1.1 per molt. First oviposition occurred at the 10th or 11th instar. Individually observed females oviposited once or twice a year, laying 6-16 eggs at one time, but females at least two years old laid 78.2 eggs per year on average in a mass-culture cage. Through this study, only females were found, and the mature females produced their progenies parthenogenetically.

Identification and Spread of the Ghost Silverfish (Ctenolepisma calvum) among Museums and Homes in Europe

Ctenolepisma calvum was first described in Sri Lanka (Ceylon) in 1910, and this island is probably the origin of this species. Later, it was also found in the Caribbean (Cuba and Trinidad and Tobago). Up until the present, it has only been identified within buildings (a synanthropic species), and its natural habitat is unknown. In 2007, it was discovered in Germany and was considered a neobiotic species of Lepismatidae in Europe. It has rapidly spread throughout Europe and beyond in recent years. This led us to analyze the available data of the first occurrences in Germany, Austria, and other European countries. Furthermore, we compared the spread inside of museums in Vienna (Austria) and Berlin (Germany). These museums have been monitored for a long period with sticky traps, representing the best source of information on the dispersion dynamics of Ctenolepisma calvum. We found a scattered occurrence of this species in 18 countries in Europe (including Russia and Ukraine). The first record for Poland has not previously been published; however, this species has been present there since 2014. Surprisingly, it was found in Hungary in 2003, but a record was only published online in 2021. Additionally, in Germany and Austria, where most data are available, the spread of the species does not follow any clear pattern. In museums in Berlin, the species has only been found in one location. In contrast, the species rapidly spread in museums in Vienna between 2014 and 2021, from four to 30 locations, and it is now a well-established species with occasional high abundance. We examined the spread of the species at three spatial scales: (i) Europe, (ii) national, and (iii) regional. Our observations indicate that it is possibly distributed with materials (packaging material, hygiene articles, paper, cardboard, and collection items). Little is yet known about the biology of this introduced pest. We describe its preferred habitat within buildings, its climate requirements, and its potential to act as a new museum pest in Central Europe. This species seems to thrive at room temperature in buildings. Further impact on the species due to climate change in the future is also discussed. We offer a simple morphological key and a detailed identification table to help correct species identification.

Climate Change and Its Effects on Indoor Pests (Insect and Fungi) in Museums

Climate change not only affects the biodiversity of natural habitats, but also the flora and fauna within cities. An increase in average temperature and changing precipitation, but additionally extreme weather events with heat waves and flooding, are forecast. The climate in our cities and, thus, also inside buildings is influenced by the changing outdoor climate and urban heat islands. A further challenge to ecosystems is the introduction of new species (neobiota). If these species are pests, they can cause damage to stored products and materials. Much cultural heritage is within buildings, so changes in the indoor climate also affect pests (insect and fungi) within the museums, storage depositories, libraries, and historic properties. This paper reviews the literature and presents an overview of these complex interactions between the outdoor climate, indoor climate, and pests in museums. Recent studies have examined the direct impact of climate on buildings and collections. The warming of indoor climates and an increased frequency or intensity of extreme weather events are two important drivers affecting indoor pests such as insects and fungi, which can severely damage collections. Increases in activity and new species are found, e.g., the tropical grey silverfish Ctenolepisma longicaudatum has been present in many museums in recent years benefitting from increased indoor temperatures.

Spatiotemporal elements in a poisoned bait strategy against the long-tailed silverfish (Lepismatidae: Zygentoma)

The long-tailed silverfish Ctenolepisma longicaudatum (Lepismatidae: Zygentoma) is a nuisance problem in buildings and a major concern in museums, libraries and archives where it cause damage to historical and priceless items. We used laboratory bioassays and two field studies of infested buildings to evaluate spatial and temporal elements of a poisoned bait strategy. In both laboratory experiments and field studies, the efficiency of poisoned bait with indoxacarb as the active ingredient was significantly improved by placing many small bait droplets evenly distributed along all edges of the treated area compared to more clustered distributions. Extended duration of bait presence and removal of competing food sources improved the control effect significantly in the laboratory bioassays. Bait-treated populations also showed a significant decline in the number of eggs deposited and emergence of new nymphs. The study supports poisoned bait as an efficient and low risk approach against the long-tailed silverfish in which extended duration of bait presence, wide distribution of bait droplets in combination with sanitation was crucial for control in the infested premises.