This data set under CC-BY license contains time series of total abundance and/or biomass of assemblages of insect, arachnid and Entognatha assemblages (grouped at the family level or higher taxonomic resolution), monitored by standardized means for ten or more years. The data were derived from 166 data sources, representing a total of 1676 sites from 41 countries. The time series for abundance and biomass represent the aggregated number of all individuals of all taxa monitored at each site. The data set consists of four linked tables, representing information on the study level, the plot level, about sampling, and the measured assemblage sizes. all references to the original data sources can be found in the pdf with references, and a Google Earth file (kml) file presents the locations (including metadata) of all datasets. When using (parts of) this data set, please respect the original open access licenses. This data set underlies all analyses performed in the paper 'Meta-analysis reveals declines in terrestrial, but increases in freshwater insect abundances', a meta-analysis of changes in insect assemblage sizes, and is accompanied by a data paper entitled 'InsectChange – a global database of temporal changes in insect and arachnid assemblages'. Consulting the data paper before use is recommended. Tables that can be used to calculate trends of specific taxa and for species richness will be added as they become available. The data set consists of four tables that are linked by the columns 'DataSource_ID'. and 'Plot_ID', and a table with references to original research. In the table 'DataSources', descriptive data is provided at the dataset level: Links are provided to online repositories where the original data can be found, it describes whether the dataset provides data on biomass, abundance or both, the invertebrate group under study, the realm, and describes the location of sampling at different geographic scales (continent to state). This table also contains a reference column. The full reference to the original data is found in the file 'References_to_original_data_sources.pdf'. In the table 'PlotData' more details on each site within each dataset are provided: there is data on the exact location of each plot, whether the plots were experimentally manipulated, and if there was any spatial grouping of sites (column 'Location'). Additionally, this table contains all explanatory variables used for analysis, e.g. climate change variables, land-use variables, protection status. The table 'SampleData' describes the exact source of the data (table X, figure X, etc), the extraction methods, as well as the sampling methods (derived from the original publications). This includes the sampling method, sampling area, sample size, and how the aggregation of samples was done, if reported. Also, any calculations we did on the original data (e.g. reverse log transformations) are detailed here, but more details are provided in the data paper. This table links to the table 'DataSources' by the column 'DataSource_ID'. Note that each datasource may contain multiple entries in the 'SampleData' table if the data were presented in different figures or tables, or if there was any other necessity to split information on sampling details. The table 'InsectAbundanceBiomassData' provides the insect abundance or biomass numbers as analysed in the paper. It contains columns matching to the tables 'DataSources' and 'PlotData', as well as year of sampling, a descriptor of the period within the year of sampling (this was used as a random effect), the unit in which the number is reported (abundance or biomass), and the estimated abundance or biomass. In the column for Number, missing data are included (NA). The years with missing data were added because this was essential for the analysis performed, and retained here because they are easier to remove than to add. Linking the table 'InsectAbundanceBiomassData.csv' with 'PlotData.csv' by column 'Plot_ID', and with 'DataSources.csv' by column 'DataSource_ID' will provide the full dataframe used for all analyses. Detailed explanations of all column headers and terms are available in the ReadMe file, and more details will be available in the forthcoming data paper. WARNING: Because of the disparate sampling methods and various spatial and temporal scales used to collect the original data, this dataset should never be used to test for differences in insect abundance/biomass among locations (i.e. differences in intercept). The data can only be used to study temporal trends, by testing for differences in slopes. The data are standardized within plots to allow the temporal comparison, but not necessarily among plots (even within one dataset).

Recent reports of dramatic declines in insect abundance suggest grave consequences for global ecosystems and human society. Most evidence comes from Europe, however, leaving uncertainty about insect population trends worldwide. We used > 5,300 time series for insects and other arthropods, collected over 4-36 years at monitoring sites representing 68 different natural and managed areas, to search for evidence of declines across the United States. Some taxa and sites showed decreases in abundance and diversity while others increased or were unchanged, yielding net abundance and biodiversity trends generally indistinguishable from zero. This lack of overall increase or decline was consistent across arthropod feeding groups, and was similar for heavily disturbed versus relatively natural sites. The apparent robustness of U.S. arthropod populations is reassuring. Yet, this result does not diminish the need for continued monitoring and could mask subtler changes in species composition that nonetheless endanger insect-provided ecosystem services.

Methods Data curated from NSF Long-Term Ecological Research Site public repositories.

Insect declines have been reported worldwide, although the particular causes of the declines may be complex and are poorly understood. Meadow spittlebugs were one of the most abundant insects in the coastal prairie along the California coast 40 years ago but have largely disappeared. Evidence links this decline to changing climatic conditions, which have reduced survival of eggs and neonates. We identified several refugia where meadow spittlebug populations have persisted amidst unfavorable conditions. Protection from desiccating winds was the common attribute of these refugia. Following a wet year, adult meadow spittlebugs were able to disperse from one refuge that we studied to recolonize coastal prairie habitats, although populations declined over the next two drier years. Because of their previous high abundance, loss of meadow spittlebugs is likely to affect the functioning of this widespread habitat, including energy transfer, their host plants, and their predators. In addition, m...

These data and code enable replication of the findings and robustness checks in "No buzz for bees: Media coverage of pollinator decline," published in Proceedings of the National Academy of Sciences of the United States of America (2020)". In this paper, we find that although widespread declines in insect biomass and diversity are increasing concern within the scientific community, it remains unclear whether attention to pollinator declines has also increased within information sources serving the general public. Examining patterns of journalistic attention to the pollinator population crisis can also inform efforts to raise awareness about the importance of declines of insect species providing ecosystem services beyond pollination. We used the Global News Index developed by the Cline Center for Advanced Social Research at the University of Illinois at Urbana-Champaign to track news attention to pollinator topics in nearly 25 million news items published by two American national newspapers and four international wire services over the past four decades. We provide a link to documentation of the Global News Index in the "relationships with articles, code, o. We found vanishingly low levels of attention to pollinator population topics relative to coverage of climate change, which we use as a comparison topic. In the most recent subset of ~10 million stories published from 2007 to 2019, 1.39% (137,086 stories) refer to climate change/global warming, while only 0.02% (1,780) refer to pollinator populations in all contexts and just 0.007% (679) refer to pollinator declines. Substantial increases in news attention were detectable only in U.S. national newspapers. We also find that while climate change stories appear primarily in newspaper “front sections”, pollinator population stories remain largely marginalized in “science” and “back section” reports. At the same time, news reports about pollinator populations increasingly link the issue to climate change, which might ultimately help raise public awareness to effect needed policy changes.

While climate warming is widely predicted to reduce body size of ectotherms, evidence for this trend is mixed. Body size depends not only on temperature but also on other factors, such as food quality and intraspecific competition. Because temperature trends or other long-term environmental factors may affect population size and food sources, attributing trends in average body size to temperature requires the separation of potentially confounding effects. We evaluated trends in the body size of the midge Tanytarsus gracilentus and potential drivers (water temperature, population size, and food quality) between 1977 and 2015 at Lake Mývatn, Iceland. Although temperatures increased at Mývatn over this period, there was only a slight (non-significant) decrease in midge adult body size, contrary to theoretical expectations. Using a state-space model including multiple predictors, body size was negatively associated with both water temperature and midge population abundance, and it was positively associated with 13C enrichment of midges (an indicator of favorable food conditions). The magnitude of these effects were similar, such that simultaneous changes in temperature, abundance, and carbon stable isotopic signature could counteract each other in the long-term body size trend. Our results illustrate how multiple factors, all of which could be influenced by global change, interact to affect average ectotherm body size. Methods Midges (Diptera: Chironomidae) were captured using window traps (Jónsson et al., 1986) at two locations around Lake Mývatn, Iceland. They were innumerated to species and separated into two cohorts (early summer and late summer), matching the voltinism pattern of the focal species (Tanytarsus gracilentus) which overwinter as larvae (Gardarsson et al., 2004; Lindegaard & Jónasson, 1979; Einarsson et al. 2002, 2004). Archived midges were used to measure carbon stable isotopes (McCormick et al. 2022) and wing lengths were measured from arculus to tip on 15-20 individuals per generation (where abundances were adequate). Because identifications of female midges is difficult and often impossible, the dataset includes only males. Air temperature data come from the Icelandic Meterological Office (https://www.vedur.is/). All processing to the data are included in scripts.

Recent reports of drastic declines in insect populations have raised global concerns about their conservation. Light pollution is a near inseparable feature of human-altered landscapes and is a potential contributing factor to insect declines. However, despite the wide recognition of the deleterious effects of lights on insects, whether these effects scale up to impact insect populations remains unclear. Here, we relied on a combination of ecological niche modeling, geographical information systems, and interviews on local ecological knowledge to assess the synergistic effects of landscape light pollution and habitat loss and fragmentation on populations of the Chocó golden scarab Chrysina argenteola. Sightings of C. argenteola by locals revealed individuals are scarcer in areas with reduced forest cover and rely on inter-patch dispersal to cope with habitat fragmentation, where they were constantly attracted to urban lights. Increasingly lit landscapes had more individuals attracted to lights, but the opposite was true in areas with less than 4 km2 of remaining forest cover. We suggest this pattern arises as landscape light pollution intercepts individuals during inter-patch dispersal. This hinders habitat connectivity, potentially disrupting metapopulation dynamics, being populations inhabiting areas with scarce fragmented habitat more vulnerable to this process. We show light pollution acts in combination with habitat loss and fragmentation in detriment of insect populations at the landscape scale.

1. Widespread population declines have been reported for diverse Mediterranean butterflies over the last three decades, and have been significantly associated to increased global change impacts. The specific landscape and climatic drivers of these declines remain uncertain for most declining species.
2. Here we analyse whether plastic phenotypic traits of a model butterfly species (Pieris napi) perform as reliable biomarkers of vulnerability to extreme temperature impacts in natural populations, showing contrasting trends in thermally exposed and thermally buffered populations.
3. We also examine whether improved descriptions of thermal exposure of insect populations can be achieved by combining multiple information sources (i.e. integrating measurements of habitat thermal buffering, habitat thermal amplification, host plant transpiration, and experimental assessments of thermal death time (TDT), thermal avoidance behaviour (TAB) and thermally induced trait plasticity). These integrat...

Statistically robust monitoring of threatened populations is essential for effective conservation management because the population trend data that monitoring generates is often used to make decisions about when and how to take action. Despite representing the highest proportion of threatened animals globally, the development of best practice methods for monitoring populations of threatened insects is relatively uncommon. Traditionally, population trend data for the Nationally Endangered New Zealand grasshopper Brachaspis robustus has been determined by counting all adults and nymphs seen on a single ~1.5 km transect searched once annually. This method lacks spatial and temporal replication, both of which are essential to overcome detection errors in highly cryptic species like B. robustus. It also provides no information about changes in the grasshopper's distribution throughout its range. Here, we design and test new population density and site occupancy monitoring protocols by comparing a) comprehensive plot and transect searches at one site and b) transect searches at two sites representing two different habitats (gravel road and natural riverbed) occupied by the species across its remaining range. Using power analyses, we determined a) the number of transects, b) the number of repeated visits and c) the grasshopper demographic to count to accurately detect long term change in relative population density. To inform a monitoring protocol design to track trends in grasshopper distribution, we estimated the probability of detecting an individual with respect to a) search area, b) weather and c) the grasshopper demographic counted at each of the two sites. Density estimates from plots and transects did not differ significantly. Population density monitoring was found to be most informative when large adult females present in early summer were used to index population size. To detect a significant change in relative density with power > 0.8 at the gravel road habitat, at least seventeen spatial replicates (transects) and four temporal replicates (visits) were required. Density estimates at the natural braided river site performed poorly and likely require a much higher survey effort. Detection of grasshopper presence was highest (p_g > 0.6) using a 100 m x 1 m transect at both sites in February under optimal (no cloud) conditions. At least three visits to a transect should be conducted per season for distribution monitoring. Monitoring protocols that inform the management of threatened species are crucial for better understanding and mitigation of the current global trends of insect decline. This study provides an exemplar of how appropriate monitoring protocols can be developed for threatened insect species.

Systemic insecticides, such as neonicotinoids, are a major contributor towards beneficial insect declines. This has led to bans and restrictions on neonicotinoid use globally, most noticeably in the Europe Union, where four commonly-used neonicotinoids are banned from outside agricultural use. While this might seem like a victory for conservation, restrictions on neonicotinoid use will only benefit insect populations if newly emerging insecticides do not have similar negative impacts on beneficial insects. Flupyradifurone and sulfoxaflor are two novel insecticides that have been registered for use globally, including within the European Union. These novel insecticides differ in their chemical class, but share the same mode of action as neonicotinoids, raising the question as to whether they have similar sub-lethal impacts on beneficial insects. Here, we conducted a systematic literature review of the potential sub-lethal impacts of these novel insecticides on beneficial insects, quantifying these effects with a meta-analysis. We demonstrate that both flupyradifurone and sulfoxaflor have significant sub-lethal impacts on beneficial insects at field-realistic levels of exposure. These results confirm that bans on neonicotinoid use will only protect beneficial insects if paired with significant changes to the agrochemical regulatory process. A failure to modify the regulatory process will result in a continued decline of beneficial insects, and the ecosystem services, on which global food production relies.

Agricultural landscapes are globally dominated by monocultures under intensive management. This is one of the main reasons for biodiversity loss and insect population decline in many regions all over the world. Agroecosystem biodiversity in these areas can be enhanced by cropping system diversification, such as crop rotations. Yet, long-term studies on effects of crop rotations on aboveground agrobiodiversity are lacking. We set up a 10-year long-term crop-rotation experiment in Central Germany and monitored the temporal dynamics of aboveground arthropods over a full cultivation period to investigate influence of current and preceding crop identity and cropping system diversification on activity density, species richness and community structure. We found that species composition was strongly influenced by currently grown crop although effect on arthropods varied between species groups. Especially winter oilseed rape strongly affects arthropod community structure. Interestingly, we were also able to show an influence of the preceding crops, indicating an ecological memory effect in aboveground arthropod community. Our results show that crop identity of both currently and previously grown crops in crop rotations may lead to an increase of arthropod activity density and changes in species composition. Diversified crop rotations including appropriate crops can be an easily implemented tool to increase arthropod biodiversity and biomass at large spatial and temporal scales, particularly in areas dominated by a single crop (e.g. wheat, maize). Our results may help to design optimized crop rotations for large-scale enhancement of insect biodiversity in agroecosystems.

As species shift their ranges and phenology to cope with climate change, many are left without a ready supply of their preferred food source during critical life stages. Food shortages are often assumed to be driven by reduced total food abundance, but here we propose that climate change may cause short-term food shortages for foraging specialists without affecting overall food availability. We frame this hypothesis around the special case of birds that forage on flying insects for whom effects mediated by their shared food resource have been proposed to cause avian aerial insectivores’ decline worldwide. Flying insects are inactive during cold, wet, or windy conditions, effectively reducing food availability to zero even if insect abundance remains otherwise unchanged. Using long-term monitoring data from a declining population of tree swallows (Tachycineta bicolor), we show that nestlings’ body mass declined substantially from 1977 to 2017. In 2017, nestlings had lower body mass if it rained during the preceding three days, though females increased provisioning rates, potentially in an attempt to compensate. Adult body mass, particularly that of the males, has also declined over the long-term study. Mean rainfall during the nestling period has increased 9.3±0.3 mm/decade, potentially explaining declining nestling body mass and population declines. Therefore, we suggest that reduced food availability, distinct from food abundance, may be an important and previously overlooked consequence of climate change, which could be affecting populations of species that specialize on foraging on flying insects.

Insect declines are a global issue with significant ecological and economic ramifications. Yet we have a poor understanding of the genomic impact these losses can have. Genome-wide data from historical specimens has the potential to provide baselines of population genetic measures to study population change, with natural history collections representing large repositories of such specimens. However, an initial challenge in conducting historical DNA data analyses, is to understand how molecular preservation varies between specimens. Here, we highlight how Next Generation Sequencing methods developed for studying archaeological samples can be applied to determine DNA preservation from only a single leg taken from entomological museum specimens, some of which are more than a century old. An analysis of genome-wide data from a set of 113 red-tailed bumblebee (Bombus lapidarius) specimens, from five British museum collections, was used to quantify DNA preservation over time. Additionally, to improve our analysis and further enable future research we generated a novel assembly of the red-tailed bumblebee genome. Our approach shows that museum entomological specimens are comprised of short DNA fragments with mean lengths below 100 base pairs (BP), suggesting a rapid and large-scale post-mortem reduction in DNA fragment size. After this initial decline, however, we find a relatively consistent rate of DNA decay in our dataset, and estimate a mean reduction in fragment length of 1.9bp per decade. The proportion of quality filtered reads mapping our assembled reference genome was around 50 %, and decreased by 1.1 % per decade. We demonstrate that historical insects have significant potential to act as sources of DNA to create valuable genetic baselines. The relatively consistent rate of DNA degradation, both across collections and through time, mean that population level analyses - for example for conservation or evolutionary studies - are entirely feasible, as long as the degraded nature of DNA is accounted for. Methods This study used an individual leg per specimen for 113 pinned B. lapidarius drones collected from 1891 to 2004. All samples were treated as degraded DNA and processed through an aDNA pipeline. Data sequenced on a NextSeq 500 and data aligned and prcoessed through bwa, samtools and picard. Linear Regression models in R.

Extending Anthophila research through image and trait digitization (Big-Bee) indexed biotic interactions and review summary. Declining populations of bees impact plant-pollinator interactions in both natural and agricultural systems. While bees and other insects pollinate most wild plants and are critical to sustaining a large proportion of global food production, they are decreasing in both numbers and diversity. Our understanding of the factors driving these declines is limited because we lack sufficient data on the distribution of bee species, and on the behavioral and anatomical traits that may make them either vulnerable or resilient to human-induced environmental changes, such as habitat loss and climate change. Fortunately, wild bees have been collected by researchers and deposited in natural history collections for over 100 years, retaining a wealth of associated attributes that can be extracted from specimen images. This project will digitally capture data and images from these historic specimens, develop tools to measure bee traits from these images and generate a comprehensive bee trait and image dataset to measure changes through time. This will increase our understanding of specific traits that put bee species at risk of decline - a critical need for both sustaining our agricultural economy and the conservation of our natural resources. In addition, the large image datasets created by this project can be used for new artificial intelligence identification tools that will help improve our future pollinator observation and monitoring efforts. The Big-Bee project began in 2021 and is funded by the National Science Foundation to mobilize data about worldwide bee species to data aggregators (e.g., iDigBio, GBIF). The Big-Bee Thematic Collection Network (Big-Bee) will create over one million high-resolution 2D and 3D images of bee specimens, representing over 5,000 worldwide bee species, including all of the major pollinating species of the United States. The Big-Bee network includes 13 institutions and partnerships with US government agencies. Novel mechanisms for sharing image datasets will be developed and datasets of bee traits will be available through an open data portal, the Bee Library, for research and education. The Big-Bee project will engage the general public in research through community science via crowdsourcing trait measurements and data transcription from images. In addition, training and professional development for natural history collection staff, researchers, and university students in data science will be provided through the creation and implementation of workshops focusing on bee traits and species identification. All data resulting from this award will be shared with and publicly available through the national digitized biocollections resource, iDigBio.org. This is the first archive of Big-Bee data indexed by Global Biotic Interactions (GloBI). GloBI provides open access to finding species interaction data (e.g., predator-prey, pollinator-plant, pathogen-host, parasite-host) by combining existing open datasets using open-source software. This version of the Big Bee dataset includes interactions that are not just bees. Also in this version, the datasets included in this publication are specifically those institutions in the Big Bee project network and do not represent all bee interaction data found at Global Biotic Interactions. Bee Library Information - Statistics about Big Bee data providers The specimens indexed by GloBI are also found in the Bee Library. To date, the number of specimens and images in the library are listed below. The Bee Library taxonomic backbone is not yet complete, so information regarding the number of species is not yet available. Further summary statistics are available in the Big Bee Metrics from the Bee Library and GloBI - July 27 2022.pdf file. From Bee Library (partner indexed records) 1,186,629 occurrence records 969,695 (82%) georeferenced 328,742 (28%) occurrences imaged 628,198 (53%) identified to species 9 families 324 genera 5,694 species 5,955 total taxa (including subsp. and var.) Collection Occurrences Georeferenced Imaged Total Taxa Interactions indexed in GloBI (bees) ASU Hasbrouck Insect Collection - Bee Records 11561 11560 1002 213 3830 Bee Biology and Systematics Laboratory, USDA-ARS Pollinating Insect-Biology, Management, Systematics Research 561820 547461 0 4698 N/A California Academy of Sciences 805 254 0 5 99 California Academy of Sciences - Type Collection 1838 52 77 1433 N/A Essig Museum of Entomology, University of California Berkeley 58543 55018 0 535 0 Florida State Collection of Arthropods 8798 8761 8252 280 0 Museum of Comparative Zoology, Harvard University 10040 9953 835 11 83 Natural History Museum of Los Angeles County 9812 4796 2546 345 0 San Diego Natural History Museum Entomology Department 2490 1616 278 173 78 University of California Santa Barbara Invertebrate Zoology Collection 8339 8103 2254 135 539...

Aim: Biodiversity loss is a major global challenge. While population trends of vertebrates are well documented, insect declines have not been sufficiently studied and their drivers are still not fully understood. This inhibits the implementation of sensible conservation action. Repeating historical surveys can help to reveal the patterns and drivers of insect declines. Location: Central Europe Time period: 2018 to 2020 Methods: We resurveyed 199 study sites in which Orthoptera assemblages had been recorded between 1986 and 1999. Results: Our results show a significant increase in species per site (α-diversity), but simultaneously a homogenization of Orthoptera assemblages (decreasing Sorensen’s β-diversity). Highly mobile species significantly increased in site occupancy compared to species with low mobility. Some Orthoptera species showed significant altitudinal range shifts, including species with positive trends (i.e. expansion to higher altitudes) and negative trends (i.e. extinctio...

Simulation outputs obtained in Vives-Ingla, M., Capdevila, P., Clements, C. F., Stefanescu, C., & Carnicer, J. (2025). Novel regimes of extreme climatic events trigger negative population rates in a common insect. Global Change Biology.

Contact:
m.vives[at]creaf.uab.cat
mariavivesingla[at]gmail.com

Abstract
The IPCC predicts that events at the extreme tail of the probability distribution will increase at a higher rate relative to less severe but still abnormal events. Such outlier events are of particular concern due to nonlinear physiological and demographic responses to climatic exposure, meaning that these events are expected to have disproportionate impacts on populations over the next decades (so called low-likelihood, high-impact events —LLHI). Because such events are historically rare, forecasting how biodiversity will respond requires mechanistic models that integrate the fundamental processes driving biological responses to our changing climate. Here we built a matrix population model (MPM) from long-term monitored populations of an insect model species in a Mediterranean area. The model simultaneously integrates the effects of extreme microclimatic heat exposure and drought-induced host-plant scarcity on early life stages, a key methodological step forward because these understudied life stages are usually very susceptible to climatic events. This model for the first time allowed us to forecast the demographic impacts that LLHI events will have on a well-known insect considering their whole life cycle. We found that juveniles were the life stage with the largest relative contribution to population dynamics. In line with field observations, simulated population rates in current climatic regimes were importantly determined by drought impacts, producing a regional mosaic of non-declining and declining populations. The simulations also indicated that, in future climate scenarios not meeting the Paris Agreement, LLHI heat extremes triggered regionally-widespread and severe declines in this currently abundant species. Our results suggest that LLHI events could thus emerge as a critical new —but overlooked— driver of the declines in insect populations, risking the crucial ecosystem functions they perform. We suggest that process-based and whole-cycle modelling approaches are a fundamental tool with which to understand the true impacts of climate change.

Contents

• _*_imp0_2024-12-10.RData: output of the main simulation set.
• elas_sens...: elasticities and sensitivities of the bootrstrapped matrices from the main simulation set.
• *_2023-07-08.RData: output without imposing a minimum pupal eclosion age.
• *_MACROCLIM_imp0_2025-01-22.RData: output without microclimatic thermal buffering effects.
• *_pred_*.RData: output with daily predation rates set at 0, 4, 7 or 8%.
• *_diflong_imp0_2025-01-25.RData: output at varying juvenile and adult longevities.
• sims_validaation...: output of simulations done over recorded microclimatic series.
• more_info_on_data.txt: more information about the variables in each data file.
  

The legend of the column names and color code are detailed in the second sheet of the file. (XLSX)

Data and manuscript of the master thesis of Jan-Lorenz Fohrmann entitled: Urban agriculture – A chance for insect diversity and food security? Pollination exclusion experiment using Sinapis alba in urban allotment gardens in Göttingen, Germany. The thesis was supervised by Prof. Catrin Westphal and Dr. Arne Wenzel from the Functional Agrobiodiversity of the University of Göttingen. Abstract: Globally, biodiversity is in decline. This is particularly alarming for insects, with reported losses of up to 75% of the biomass. At the same time, insects provide important ecosystem services, for example as pollinators. Among the discussed drivers of diversity decline is urbanization. Currently, half of the world’s population live in or near cities, which keep expanding with no indication of an end. Besides their role as living and working space, cities are also a place of food production. Urban agriculture is growing in importance, especially in developing regions, which are also the hotspots of urbanization and, in many cases, biodiversity. Still, urban agriculture can also reduce the environmental footprint of food production in developed regions. There is no clear consensus on the role urbanization plays for the abundance and diversity of pollinating insects. Alongside negative, neutral and even positive responses have been reported. Therefore, for my master thesis, I conducted a pollination exclusion experiment in eight garden allotments around the city of Göttingen, Germany, to evaluate how the surrounding land-use and grade of urbanization affects the pollinator community. For this, I cultivated Sinapis alba-plants in the green house until they induced flowering, and then transported them to the study sites. While some plants were given access to pollinators, others were excluded with a net. I then observed the insects visiting the study plants and those that were overall present in the gardens before the plants were brought back to the greenhouse and harvested to get an impression of their reproductive success. Additionally, I derived the surrounding land-use from satellite imagery using QGIS, and assessed local characteristics of each garden, such as flower abundance and nesting resources. The results point out that well managed urban green spaces can attract a large and healthy pollinator community. At least 72 taxa of flower-visiting insects were observed on my study plants, and the plants’ reproductive output did not seem to be impaired. However, while the number of visitors was even increasing with urbanization, their richness was negatively affected, indicating a dominant role of fewer generalist species in highly urbanized areas. Also, unlike suggested by several other studies, local effects such as flowering and nesting resources did not seem to overshadow the effect of larger-scale landscape characteristics, as both types of models showed similar amounts of significant relationships. Still, abundant floral resources and a high proportion of open soil seemed to positively affect pollinator activity. Urban pollinators put high-priority and high-impact biodiversity conservation within reach of a large proportion of the human population. Allotment gardens have shown to be a highly attractive habitat for insect pollinators, as they provide continuous floral resources and various nesting opportunities, and the observed pollinator communities included large, attractive species like Andrena agilissima and Xylocopa violacea. Insect conservation is of great popularity and can be achieved with relatively little effort, by providing adequate floral and nesting resources. The allotment gardeners I worked with showed great awareness and knowledge of this and often considered themselves agents of insect conservation. Therefore, for future research in the field of urban pollinators, citizen science can be a very promising approach.

Concerns about widespread human-induced declines in insect populations are mounting, yet little is known about how land-use change modifies the dynamics of insect communities, particularly in understudied regions. Here, we examine how the seasonal activity patterns of ants—key drivers of terrestrial ecosystem functioning—vary with anthropogenic land-cover change on a subtropical island landscape, and whether differences in temperature or species composition can explain observed patterns. Using trap captures sampled biweekly over two years from a biodiversity monitoring network covering Okinawa Island, Japan, we processed 1.2 million individuals and reconstructed activity patterns within and across habitat types. Forest communities exhibited greater temporal variability of activity than those in more developed areas. Using time-series decomposition to deconstruct this pattern, we found that sites with greater human development exhibited ant communities with diminished seasonality, reduced synchrony, and higher stochasticity compared to sites with greater forest cover. Our results cannot be explained by variation in regional or site temperature patterns, or by differences in species richness or composition among sites. Our study raises the possibility that disruptions to natural seasonal patterns of functionally key insect communities may comprise an important and underappreciated consequence of global environmental change that must be better understood across Earth’s biomes. Methods The ant activity data used in the analysis was collected with Sea, Land, and Air Malaise (SLAM) traps on Okinawa Island in Japan from 2016-2018, and was processed using the code provided in the Zenodo archive (see README for links and the paper for references). Other datasets come from the Japan Meterological Agency (JMA), in situ climate variables for sampling stations measured on-site, and land-cover data for Okinawa developed by our team. The data used in the analysis is included in the data upload (with JMA and land-cover data files in a Zenodo supplemental information under the CC-By 4 license), and all the analysis code is included in the R package provided in a separate Zenodo software archive. NOTE: All datasets (from Dryad and Zenodo) must be put into a single folder called /data within the main directory of the R analysis package before running any code. Please consult the README for further details on the data and code.

Tropical ectotherms are particularly vulnerable to global warming because their physiologies are assumed to be adapted to narrow temperature ranges. This study explores three mechanisms potentially constraining thermal adaptation to global warming in tropical insects: 1. tradeoffs in genotypic performance at different temperatures (the jack-of-all-trades hypothesis) 2. positive genetic covariance in performance, with some genotypes performing better than others at viable temperatures (the 'winner and 'loser genotypes hypothesis) or 3. limited genetic variation as the potential result of relaxed selection and the loss of genes associated with responses to extreme temperatures (the gene decay hypothesis). We estimated changes in growth and survival rates at multiple temperatures for three tropical rain forest insect herbivores (Cephaloleia rolled-leaf beetles, Chrysomelidae). We reared 2746 individuals in a full-sibling experimental design, at temperatures known to be experienced by this genus of beetles in nature (i.e., 10-35°C). Significant genetic covariance was positive for 16 traits, supporting the 'winner and 'loser genotypes hypothesis. Only two traits displayed negative cross-temperature performance correlations. We detected a substantial contribution of genetic variance in traits associated with size and mass (0-44%), but low heritability in plastic traits such as development time (0-6%) or survival (0-4%). Lowland insect populations will most likely decline if current temperatures increase beyond 2°C. It is concerning that local adaption is already lagging behind current temperatures. The consequences of maintaining the current global warming trajectory would be devastating for tropical insects. However, if humans can limit or slow warming, many tropical ectotherms might persist in their current locations, and potentially adapt to warmer temperatures.

Global declines in insect abundance are of significant concern. While there is evidence that climate change is contributing to insect declines, we know little of the direct mechanisms responsible for these declines. Male fertility is compromised by increasing temperatures, and the thermal limit to fertility has been implicated as an important factor in the response of insects to climate change. However, climate change is affecting both temperature and hydric conditions, and the effects of water availability on male fertility have rarely been considered. Here we exposed male crickets Teleogryllus oceanicus to either low- or high-humidity environments while holding temperature constant. We measured water loss and the expression of both pre- and post-mating reproductive traits. Males exposed to a low-humidity environment lost more water than males exposed to a high-humidity environment. A male's cuticular hydrocarbon profile (CHC) did not affect the amount of water lost, and males did not adjust the composition of their CHC profiles in response to hydric conditions. Males exposed to a low-humidity environment were less likely to produce courtship song or produced songs of low quality. Their spermatophores failed to evacuate and their ejaculates contained sperm of reduced viability. The detrimental effects of low humidity on male reproductive traits will compromise male fertility and population persistence. We argue that limits to insect fertility based on temperature alone are likely to underestimate the true effects of climate change on insect persistence, and that the explicit incorporation of water regulation into our modelling will yield more accurate predictions of the effects of climate change on insect declines.