The contribution of insects to global forest deadwood decomposition.

The amount of carbon stored in deadwood is equivalent to about 8 per cent of the global forest carbon stocks1. The decomposition of deadwood is largely governed by climate2-5 with decomposer groups-such as microorganisms and insects-contributing to variations in the decomposition rates2,6,7. At the global scale, the contribution of insects to the decomposition of deadwood and carbon release remains poorly understood7. Here we present a field experiment of wood decomposition across 55 forest sites and 6 continents. We find that the deadwood decomposition rates increase with temperature, and the strongest temperature effect is found at high precipitation levels. Precipitation affects the decomposition rates negatively at low temperatures and positively at high temperatures. As a net effect-including the direct consumption by insects and indirect effects through interactions with microorganisms-insects accelerate the decomposition in tropical forests (3.9% median mass loss per year). In temperate and boreal forests, we find weak positive and negative effects with a median mass loss of 0.9 per cent and -0.1 per cent per year, respectively. Furthermore, we apply the experimentally derived decomposition function to a global map of deadwood carbon synthesized from empirical and remote-sensing data, obtaining an estimate of 10.9 ± 3.2 petagram of carbon per year released from deadwood globally, with 93 per cent originating from tropical forests. Globally, the net effect of insects may account for 29 per cent of the carbon flux from deadwood, which suggests a functional importance of insects in the decomposition of deadwood and the carbon cycle.

DNA metabarcoding reveals host-specific communities of arthropods residing in fungal fruit bodies.

Biological communities within living organisms are structured by their host's traits. How host traits affect biodiversity and community composition is poorly explored for some associations, such as arthropods within fungal fruit bodies. Using DNA metabarcoding, we characterized the arthropod communities in living fruit bodies of 11 wood-decay fungi from boreal forests and investigated how they were affected by different fungal traits. Arthropod diversity was higher in fruit bodies with a larger surface area-to-volume ratio, suggesting that colonization is crucial to maintain arthropod populations. Diversity was not higher in long-lived fruit bodies, most likely because these fungi invest in physical or chemical defences against arthropods. Arthropod community composition was structured by all measured host traits, namely fruit body size, thickness, surface area, morphology and toughness. Notably, we identified a community gradient where soft and short-lived fruit bodies harboured more true flies, while tougher and long-lived fruit bodies had more oribatid mites and beetles, which might reflect different development times of the arthropods. Ultimately, close to 75% of the arthropods were specific to one or two fungal hosts. Besides revealing surprisingly diverse and host-specific arthropod communities within fungal fruit bodies, our study provided insight into how host traits structure communities.

Legacies of invertebrate exclusion and tree secondary metabolites control fungal communities in dead wood.

During decomposition of organic matter, microbial communities may follow different successional trajectories depending on the initial environment and colonizers. The timing and order of the species arrival (assembly history) can lead to divergent communities through priority effects. We explored how assembly history and resource quality affected fungal communities and decay rate of decomposing wood, 1.5 and 4.5 years after tree felling. Additionally, we investigated the effect of invertebrate exclusion during the first two summers. We measured initial resource quality of bark and wood of aspen (Populus tremula) logs and surveyed the fungal communities by DNA metabarcoding at different times during succession. We found that gradients in fungal community composition were related to resource quality and we discuss how this may reflect different fungal life history strategies. As with previous studies, the initial amount of bark tannins was negatively correlated with wood decomposition rate over 4.5 years. The initial fungal community explained variation in community composition after 1.5, but not 4.5, years of succession. Although the assembly history of initial colonizers may cause alternative trajectories in successional communities, our results indicate that the communities may converge with the arrival of secondary colonizers. We also identified a strong legacy of invertebrate exclusion on fungal communities, even after 4.5 years of succession, thereby adding crucial knowledge on the importance of invertebrates in affecting fungal community development. By measuring and manipulating aspects of assembly history and resource quality that have rarely been studied, we expand our understanding of the complexity of fungal community dynamics.

Disentangling phylogenetic relations and biogeographic history within the Cucujus haematodes species group (Coleoptera: Cucujidae).

Recent progress in the taxonomy of flat bark beetles (Cucujidae), specifically, in the genus Cucujus, has revealed great diversity in subtropical Asia, but the seemingly well-known temperate and boreal taxa need further attention because of their conservation status. Here, we used an integrative approach using morphology, DNA, and species distribution modelling to disentangle phylogenetic relations, verify the number of species, and understand the historical biogeography of Palearctic and Nearctic Cucujus beetles, particularly the C. haematodes species group. Species distinctiveness was supported for C. cinnaberinus, but present-day C. haematodes turned out to be a species complex made up of separate lineages in the western, middle and eastern parts of its Palearctic range. Cucujus muelleri was a member of that complex, being sister to Asian C. haematodes. Moreover, C. haematodes caucasicus was found to be phylogenetically closely related to Italian C. tulliae, and both to be sister to European C. haematodes. North American C. clavipes clavipes and C. c. puniceus resulted to be enough divergent to be considered different species. Interestingly, western American C. puniceus turned out to be closely related to the C. haematodes complex, whereas eastern American C. clavipes constituted a separate lineage, being distantly related to both C. puniceus and C. cinnaberinus. These patterns suggest former trans-continental connections among the ancestors of extant flat bark beetle species. Moreover, a divergent lineage of C. cinnaberinus was found in Calabria, which should be regarded at the very least as a subspecies. The ancestor of C. hameatodes group originated in mid-Miocene, and next, ca. 6.2 Mya, a line leading to C. cinnaberinus had split. Speciation of the American lineages occurred during Pliocene (4.4 Mya for C. clavipes and 3.3 Mya for C. puniceus). Species classified as C. haematodes, C. tulliae and C. muelleri, as well as distinct lineages within C. cinnaberinus split during mid Pleistocene (ca. 1.5 Mya). A comparison of species climatic requirements and their present distribution allowed to identify glacial refugia in south-eastern areas of North America (C. clavipes), south-western areas of North America (C. puniceus), and the Mediterranean and Caspian Sea Basins (European Cucujus species), or south-eastern areas of Asia and the foothills of the central Asian mountains (eastern C. haematodes). Subsequent climatic changes in the Holocene forced these beetles to move their ranges northwards along the coasts of the Pacific (C. puniceus) or Atlantic (C. clavipes), north-eastwards to central, northern, and eastern Europe (C. cinnaberinus and European C. haematodes) or Siberia (Asian C. haematodes). The combined use of molecular, morphological and climatic data allows a comprehensive understanding of the phylogenetic relations and past distributions of Cucujus beetles, highlighting the complexity of C. haematodes species group evolution.

Pesticide effects on the abundance of springtails and mites in field mesocosms at an agricultural site.

The use of pesticides to protect crops often affects non-target organisms vital to ecosystem functioning. A functional soil mesofauna is important for decomposition and nutrient cycling processes in agricultural soils, which generally have low biodiversity. To assess pesticide effects on natural soil communities we enclosed intact soil cores in situ in an agricultural field in 5 cm wide mesocosms. We used two types of mesh lids on the mesocosms, allowing or preventing migration of mesofauna. The mesocosms were exposed to the insecticide imidacloprid (0, 0.1, 1, and 10 mg/kg dry soil) and left in the field for 20 days. Overall, regardless of lid type, mesocosm enclosure did not affect springtail or mite abundances during the experiment when compared with undisturbed soil. Imidacloprid exposure reduced the abundance of both surface- and soil-living springtails in a concentration-dependent manner, by 65-90% at the two highest concentrations, and 21-23% at 0.1 mg/kg, a concentration found in some agricultural soils after pesticide application. Surface-living springtails were more affected by imidacloprid exposure than soil-living ones. In contrast, neither predatory nor saprotrophic mites showed imidacloprid-dependent changes in abundance, concurring with previous findings indicating that mites are generally less sensitive to neonicotinoids than other soil organisms. The possibility to migrate did not affect the springtail or mite abundance responses to imidacloprid. We show that under realistic exposure concentrations in the field, soil arthropod community composition and abundance can be substantially altered in an organism-dependent manner, thus affecting the soil community diversity.

What does a threatened saproxylic beetle look like? Modelling extinction risk using a new morphological trait database.

The extinction of species is a non-random process, and understanding why some species are more likely to go extinct than others is critical for conservation efforts. Functional trait-based approaches offer a promising tool to achieve this goal. In forests, deadwood-dependent (saproxylic) beetles comprise a major part of threatened species, but analyses of their extinction risk have been hindered by the availability of suitable morphological traits. To better understand the mechanisms underlying extinction in insects, we investigated the relationships between morphological features and the extinction risk of saproxylic beetles. Specifically, we hypothesised that species darker in colour, with a larger and rounder body, a lower mobility, lower sensory perception and more robust mandibles are at higher risk. We first developed a protocol for morphological trait measurements and present a database of 37 traits for 1,157 European saproxylic beetle species. Based on 13 selected, independent traits characterising aspects of colour, body shape, locomotion, sensory perception and foraging, we used a proportional-odds multiple linear mixed-effects model to model the German Red List categories of 744 species as an ordinal index of extinction risk. Six out of 13 traits correlated significantly with extinction risk. Larger species as well as species with a broad and round body had a higher extinction risk than small, slim and flattened species. Species with short wings had a higher extinction risk than those with long wings. On the contrary, extinction risk increased with decreasing wing load and with higher mandibular aspect ratio (shorter and more robust mandibles). Our study provides new insights into how morphological traits, beyond the widely used body size, determine the extinction risk of saproxylic beetles. Moreover, our approach shows that the morphological characteristics of beetles can be comprehensively represented by a selection of 13 traits. We recommend them as a starting point for functional analyses in the rapidly growing field of ecological and conservation studies of deadwood.

Parasitoids indicate major climate-induced shifts in arctic communities.

Climatic impacts are especially pronounced in the Arctic, which as a region is warming twice as fast as the rest of the globe. Here, we investigate how mean climatic conditions and rates of climatic change impact parasitoid insect communities in 16 localities across the Arctic. We focus on parasitoids in a widespread habitat, Dryas heathlands, and describe parasitoid community composition in terms of larval host use (i.e., parasitoid use of herbivorous Lepidoptera vs. pollinating Diptera) and functional groups differing in their closeness of host associations (koinobionts vs. idiobionts). Of the latter, we expect idiobionts-as being less fine-tuned to host development-to be generally less tolerant to cold temperatures, since they are confined to attacking hosts pupating and overwintering in relatively exposed locations. To further test our findings, we assess whether similar climatic variables are associated with host abundances in a 22 year time series from Northeast Greenland. We find sites which have experienced a temperature rise in summer while retaining cold winters to be dominated by parasitoids of Lepidoptera, with the reverse being true for the parasitoids of Diptera. The rate of summer temperature rise is further associated with higher levels of herbivory, suggesting higher availability of lepidopteran hosts and changes in ecosystem functioning. We also detect a matching signal over time, as higher summer temperatures, coupled with cold early winter soils, are related to high herbivory by lepidopteran larvae, and to declines in the abundance of dipteran pollinators. Collectively, our results suggest that in parts of the warming Arctic, Dryas is being simultaneously exposed to increased herbivory and reduced pollination. Our findings point to potential drastic and rapid consequences of climate change on multitrophic-level community structure and on ecosystem functioning and highlight the value of collaborative, systematic sampling effort.

Environmental conditions alter successional trajectories on an ephemeral resource: a field experiment with beetles in dead wood.

Successional processes can be observed for many organisms and resources, but most studies of succession have focused on plants. A general framework has been proposed, advocating that successional patterns in species turnover are predominantly driven by competition, dispersal or abiotic limitation, and that the patterning of species accumulation over time gives clues to which process is most influential in a given system. We applied this framework to succession in communities of wood-living beetles, utilizing ephemeral resources in the form of 60 experimentally created dead aspen high stumps. High stumps were created at sun-exposed sites (high ambient temperature; favourable abiotic conditions) and shaded sites (low ambient temperature; abiotically limiting conditions). The sites were intermixed, ensuring similar dispersal opportunities. Beetle species richness and abundance were monitored with flight interception traps over four consecutive years. Consistent with predictions from the tested framework, several beetle functional groups accumulated species more slowly at the unfavourable shaded sites than at the favourable exposed sites. Species richness at the exposed sites increased rapidly to a plateau, consistent with a limiting effect of competition on community development. Similar results were obtained for beetle abundance and community structure. Part of the variance in beetle community structure was jointly explained by habitat and fungal community composition, suggesting that differences in the composition and developmental rate of fungal communities in the two habitats contributed to the observed patterns. Targeted experimental studies are now required to decisively establish what processes underlie the contrasting successional trajectories in the two environments.

Revealing hidden insect-fungus interactions; moderately specialized, modular and anti-nested detritivore networks.

Ecological networks are composed of interacting communities that influence ecosystem structure and function. Fungi are the driving force for ecosystem processes such as decomposition and carbon sequestration in terrestrial habitats, and are strongly influenced by interactions with invertebrates. Yet, interactions in detritivore communities have rarely been considered from a network perspective. In the present study, we analyse the interaction networks between three functional guilds of fungi and insects sampled from dead wood. Using DNA metabarcoding to identify fungi, we reveal a diversity of interactions differing in specificity in the detritivore networks, involving three guilds of fungi. Plant pathogenic fungi were relatively unspecialized in their interactions with insects inhabiting dead wood, while interactions between the insects and wood-decay fungi exhibited the highest degree of specialization, which was similar to estimates for animal-mediated seed dispersal networks in previous studies. The low degree of specialization for insect symbiont fungi was unexpected. In general, the pooled insect-fungus networks were significantly more specialized, more modular and less nested than randomized networks. Thus, the detritivore networks had an unusual anti-nested structure. Future studies might corroborate whether this is a common aspect of networks based on interactions with fungi, possibly owing to their often intense competition for substrate.

Head lice predictors and infestation dynamics among primary school children in Norway.

BACKGROUND: Health providers need to know which measures to take and children to prioritize in order to decrease costs associated with head lice infestations. OBJECTIVE: Our aim was to determine the most important predictors for head lice and identify the major drivers of an infestation outbreak in a low-prevalence area. METHODS: The study was based on three datasets of head lice prevalence (retrospective, point prevalence and prospective approach) from primary school children (ages 6-12) at 12 schools in Oslo, Norway. The tested predictors were siblings with lice, individual and household characteristics as well as class and school affiliation. Self-reported monthly incidences (prospective approach) of head lice were used to evaluate infestation dynamics. RESULTS: Infested siblings strongly increased the odds of head lice infestation of school children (odds ratio 36, 26 and 7 in the three datasets) whereas having short hair halved the odds. Household characteristics were of minor importance, and class affiliation proved more important than school affiliation. Having head lice in one school term increased the odds of an infestation in the next, but this effect diminished over time. About 97% of all self-reported infestations were noted in two consecutive months or less. CONCLUSIONS: With the exception of hair length, we have found that individual and household characteristics are of minor importance to predict head lice infestations in a low-prevalence country and that unnoticed transmissions in school classes and families are likely to be the major driver upon outbreaks.

Effect of Habitat Size, Quality, and Isolation on Functional Groups of Beetles in Hollow Oaks.

One of the largest threats to biodiversity is land use change and habitat loss. Hollow oaks (Quercus spp. L.) are well-defined patches that are hotspots for biodiversity and red-listed species, but they are often rare and fragmented in the landscape. We investigated the effect of patch size, habitat quality, and isolation on functional groups and red-listed saproxylic beetles in hollow oaks (n = 40) in Norway. The groups were defined by host tree association, trophic grouping, and red-listed status. Habitat quality, represented by tree form was most important in explaining species richness for most groups. Patch size, represented by circumference and amount of dead branches, was most important in explaining abundance. Isolation, that is single oaks compared with oaks in groups, had a negative effect on the abundance of beetles feeding both on wood and fungi (xylomycethopagous), as well as on species associated with broadleaved trees (oak semi-specialists), but did not affect species richness. This indicates that at this scale and in this landscape, isolated oaks are as species rich and valuable for conservation as other oaks, although some functional groups may be more vulnerable to isolation than others. The red-listed species only responded to patch size, indicating that oaks with large circumference and many dead branches are especially important for red-listed species and for conservation.

Socioeconomic status, family background and other key factors influence the management of head lice in Norway.

How head lice infestations are managed by households is an important but generally neglected issue in head lice research. In the present study, we investigate actions taken against head lice by Norwegian households in association with socioeconomic status, family background, school-related variables and other key factors. Repeat questionnaires distributed to caretakers of the same elementary school children during a 2-year period enabled us to study both previous head lice management and any changes in this management through time. Households from 12 schools spanning the main socioeconomic variation found in Norway participated in the study. All students with active head lice infestation were treated in the four investigated periods. Most caretakers used a thorough head lice checking technique and informed others of own infestation. Checking frequency was low as most children were inspected less than monthly. The best determinant of increased checking frequency and thoroughness was personal experience with head lice. The increased awareness, however, seemed to be somewhat short-lived, as there was a decrease in checking frequency and thoroughness within 1 year after infestation. Personal experience with head lice also increased general knowledge related to the parasite. Parents born in developing countries checked their children for head lice more frequently, although less thoroughly, informed fewer contacts when infested, used pediculicides preventively more often and knew less about head lice than parents born in developed countries. Households with highly educated mothers had a lower checking frequency, but their knowledge and willingness to inform others was high. Single parents were more concerned about economic costs and kept children home from school longer while infested than other parents. As head lice management varied among socioeconomic groups and with parental background, differentiated advice should be considered in the control of head lice. The biannual focus on head lice during the 2 years of investigation increased checking thoroughness, while checking frequency remained unchanged. Based on the results, we suggest new head lice management guidelines for health authorities.

Trophic food chain transfer of radiocaesium from reindeer meat to the blowfly Calliphora vicina and the parasitoid wasp Nasonia vitripennis.

The role of insects in the transfer of radionuclides has received little attention, despite their key role in nutrient cycling within ecosystems. In this study, we investigated the trophic food chain transfer of radiocaesium (137Cs) from reindeer meat to the blowfly Calliphora vicina (Robineau-Desvoidy) (Diptera: Calliphoridae) and further from blowfly pupae to the parasitoid wasp Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae). Radiocaesium was transferred to blowfly larvae during their feeding stage, with the highest whole-organism to food source concentration ratios (CRwo-fs) being found in actively feeding third instar blowfly larvae, with CRwo-fs in the range of 0.68-0.90. CRwo-fs in blowfly larvae at later developmental stages (i.e., post-feeding stage, prepupal stage, pupal stage, and adult stage) were significantly lower, with CRwo-fs in adult flies in the range of 0.07-0.10. Modelling of the data indicated that >70 % of the radiocaesium present in third instar feeding stage larvae was removed exponentially with excreta prior to pupariation. Furthermore, on average 49 % of the radiocaesium activity concentration assimilated in the metamorphing blowfly pupa was retained in the pupal case after the adult blowfly had emerged. When blowfly pupae were parasitised by parasitoid wasps, a greater proportion of radiocaesium was retained in the parasitised pupal case, with only 2-3 % of the activity concentration in the meat being found in the wasps, providing further evidence to support that radiocaesium is biodiluted in insect food chains. Our results indicate that carcass decomposition driven by insects directly affects the fate of radiocaesium retained in vertebrate carcasses and we discuss these findings in connection to radiocaesium cycling and dispersion in terrestrial ecosystems.

Saproxylic beetles' morphological traits and higher trophic guilds indicate boreal forest naturalness.

Forests contribute to numerous ecosystem functions and services and contain a large proportion of terrestrial biodiversity, but they are being negatively impaced by anthropogenic activities. Forests that have never been clear-cut and have old growth characteristics, termed "near-natural," often harbor different and richer species assemblages than managed forests. Alternative management strategies may be able to balance the needs of biodiversity with the demands of forestry, but evaluation efforts are limited by the challenges of measuring biodiversity. Species richness is frequently used as a simple measure of biodiversity, but research indicates that it may not adequately capture community-level changes. Alternatively, trait-based measures of biodiversity may prove to be useful, but research is lacking. In this paper, we use a large dataset that includes 339 obligate saproxylic beetle species collected over a decade in the boreal region throughout southern Norway to: (1) establish if there is a difference in beetle community composition between near-natural and managed forests; and (2) determine which measures of beetle biodiversity best indicate forest naturalness. We arranged the sites in an ordination space and tested for differences in community composition between these forest types. We also tested different measures of biodiversity to determine which were the most predictive of forest naturalness. We found a clear difference in community composition between near-natural and managed forests. Additionally, three measures of biodiversity were most predictive of forest naturalness: proportional abundance of predators, community weighted mean (CWM) of wing length, and CWM of body roundness. The probability that a forest was near-natural increased with the proportional abundance of predators but decreased with CWM wing length and body roundness. Although species richness was higher in near-natural forests, the effect was not significant. Overall, our findings underscore the conservation value of near-natural forests and highlight the potential of several measures of biodiversity for determining forest quality.

Alternative measures of trait-niche relationships: A test on dispersal traits in saproxylic beetles.

Functional trait approaches are common in ecology, but a lack of clear hypotheses on how traits relate to environmental gradients (i.e., trait-niche relationships) often makes uncovering mechanisms difficult. Furthermore, measures of community functional structure differ in their implications, yet inferences are seldom compared among metrics. Community-weighted mean trait values (CWMs), a common measure, are largely driven by the most common species and thus do not reflect community-wide trait-niche relationships per se. Alternatively, trait-niche relationships can be estimated across a larger group of species using hierarchical joint species distribution models (JSDMs), quantified by a parameter Γ. We investigated how inferences about trait-niche relationships are affected by the choice of metric. Using deadwood-dependent (saproxylic) beetles in fragmented Finnish forests, we followed a protocol for investigating trait-niche relationships by (1) identifying environmental filters (climate, forest age, and deadwood volume), (2) relating these to an ecological function (dispersal ability), and (3) identifying traits related to this function (wing morphology). We tested 18 hypothesized dispersal relationships using both CWM and Γ estimates across these environmental gradients. CWMs were more likely than Γ to show support for trait-niche relationships. Up to 13% of species' realized niches were explained by dispersal traits, but the directions of effects were consistent with fewer than 11%-39% of our 18 trait-niche hypotheses (depending on the metric used). This highlights the difficulty in connecting morphological traits and ecological functions in insects, despite the clear conceptual link between landscape connectivity and flight-related traits. Caution is thus warranted in hypothesis development, particularly where apparent trait-function links are less clear. Inferences differ when CWMs versus Γ estimates are used, necessitating the choice of a metric that reflects study questions. CWMs help explain the effects of environmental gradients on community trait composition, whereas the effects of traits on species' niches are better estimated using hierarchical JSDMs.

High-resolution 3D forest structure explains ecomorphological trait variation in assemblages of saproxylic beetles.

Climate, topography and the 3D structure of forests are major drivers affecting local species communities. However, little is known about how the specific functional traits of saproxylic (wood-living) beetles, involved in the recycling of wood, might be affected by those environmental characteristics.Here, we combine ecological and morphological traits available for saproxylic beetles and airborne laser scanning (ALS) data in Bayesian trait-based joint species distribution models to study how traits drive the distributions of more than 230 species in temperate forests of Europe.We found that elevation (as a proxy for temperature and precipitation) and the proportion of conifers played important roles in species occurrences while variables related to habitat heterogeneity and forest complexity were less relevant. Furthermore, we showed that local communities were shaped by environmental variation primarily through their ecological traits whereas morphological traits were involved only marginally. As predicted, ecological traits influenced species' responses to forest structure, and to other environmental variation, with canopy niche, wood decay niche and host preference as the most important ecological traits. Conversely, no links between morphological traits and environmental characteristics were observed. Both models, however, revealed strong phylogenetic signal in species' response to environmental characteristics.These findings imply that alterations of climate and tree species composition have the potential to alter saproxylic beetle communities in temperate forests. Additionally, ecological traits help explain species' responses to environmental characteristics and thus should prove useful in predicting their responses to future change. It remains challenging, however, to link simple morphological traits to species' complex ecological niches. Read the free Plain Language Summary for this article on the Journal blog.

Head lice prevalence among households in Norway: importance of spatial variables and individual and household characteristics.

Head lice prevalence varies greatly between and within countries, and more knowledge is needed to approach causes of this variation. In the present study, we investigated head lice prevalence among elementary school students and their households in relation to individual and household characteristics as well as spatial variables. The investigation included households from 5 geographically separated municipalities. Present infestations among household members as well as previous infestations in the household were reported in a questionnaire. In elementary school students prevalence was low (1·63%), but more than one-third of the households (36·43%) had previously experienced pediculosis. Prevalence was higher in elementary school students than in other household members, and highest in third-grade children. Prevalence was also influenced by the school attended, which suggested that interactions between children in the same school are important for head lice transmission. Previous occurrence of head lice in homes also increased the risk of present infestation. Prevalence of previous infestations was higher in households with more children and in more densely populated municipalities, indicating that the density of hosts or groups of hosts influences transmission rates. These results demonstrate that information of hosts' spatial distribution as well as household and individual characteristics is needed to better understand head lice population dynamics.

Efficient mass trapping: catching the pest, Calliphora vicina, (Diptera, Calliphoridae), of Norwegian stockfish production.

Attracting high numbers of adult females, extensive trapping prior to damage, and a pest species with a predominantly univoltine lifecycle, are important factors contributing to the success of mass-trapping programs. We conducted a mass-trapping experiment over 4 years, using yellow sticky traps and odor-baited funnel traps for control of the blowfly Calliphora vicina in stockfish production areas in Loften, Norway. Blowfly-related damage to fish in five mass-trapping sites was compared with damage at five control sites. Population monitoring established a connection between blowfly activity and damage. Blowfly activity in the period from mid-April to mid-May was correlated with damage to fish in the same year. Interception (sticky) traps, based on visual cues, caught blowflies during the early drying period, whereas odor-baited funnel traps were more effective during the later drying period, and continued to catch flies throughout the year until late autumn. In the funnel traps, 80% of the captured flies were females. Compared to control sites, mass trapping reduced overall damage to stockfish by 8-31%. In the final year of the experiment, we compared mass-trapping and control treatments, controlling for drying time period and sun exposure (which both contribute to damage), and found a damage reduction of 63%. Thus, mass-trapping with a female-attracting kairomone, and using traps of different functionality to extend the critical trapping period, in accord with pest phenology, is an efficient method for control of C. vicina in stockfish production.

Veteran trees have divergent effects on beetle diversity and wood decomposition.

Veteran hollow trees are keystone structures in ecosystems and provide important habitat for a diverse set of organisms, many of which are involved in the process of decomposition. Since veteran trees are 'islands' of high biodiversity, they provide a unique system in which to study the relationship between biodiversity and decomposition of wood. We tested this relationship with a balanced experiential design, where we quantified the taxonomic and functional diversity of beetles directly involved in the process of decomposing wood, and measured the decomposition of experimentally added bundles of small diameter wood around 20 veteran trees and 20 nearby young trees in southern Norway. We found that the diversity (both taxonomic and functional) of wood-decomposing beetles was significantly higher around the veteran trees, and beetle communities around veteran trees consisted of species with a greater preference for larger diameter wood. We extracted few beetles from the experimentally added wood bundles, regardless of the tree type that they were placed near, but decomposition rates were significantly lower around veteran trees. We speculate that slower decomposition rates around veteran trees could have been a result of a greater diversity of competing fungi, which has been found to decrease decay rates. Veteran trees provide an ecological legacy within anthropogenic landscapes, enhance biodiversity and influence wood decomposition. Actions to protect veteran trees are urgently needed in order to save these valuable organisms and their associated biodiversity.

Veteran trees are a source of natural enemies.

Predation of invertebrate pest by natural enemies is a critical contribution of nature to people, because invertebrate pests cause a vast amount of economic damage and pesticides use has many long-term costs. Veteran trees are keystone structures and hotspots for biodiversity, and are a potential source of natural enemies. To explore this, we used a balanced experimental design where we measured predatory beetle diversity and attack marks on three colors of artificial caterpillars placed around 20 veteran oaks and 20 nearby young oaks, in Southern Norway. We predicted that around the veteran oaks there would be a greater diversity of predatory beetles and more invertebrate attacks on artificial caterpillars. Sampling for predatory beetles was conducted in summer 2017 and 2018, and invertebrate attacks were measured in 2018. We found support for the predictions: diversity of predatory beetles was higher around veteran trees and there were more arthropod attack marks on artificial caterpillars placed around veteran trees. Our results indicated that veteran trees are a source of natural enemies. Valuing and protecting veteran trees and their communities is an essential step towards a more sustainable system of management that has the possibility of promoting both the wellbeing of people and biodiversity.