Wireworms, the larvae of click beetles (Coleoptera: Elateridae), have had a centuries-long role as major soil insect pests worldwide. With insecticidal control options dwindling, research on click beetle biology and ecology is of increasing importance in the development of new control tactics. Methodological improvements have deepened our understanding of how larvae and adults spatially and temporarily utilize agricultural habitats and interact with their environment. This progress, however, rests with a few pest species, and efforts to obtain comparable knowledge on other economically important elaterids are crucial. There are still considerable gaps in our understanding of female and larval ecology; movement of elaterids within landscapes; and the impact of natural enemies, cultivation practices, and environmental change on elaterid population dynamics. This knowledge will allow generation of multifaceted control strategies, including cultural, physical, and chemical measures, tailored toward species complexes and crops across a range of appropriate spatial scales.

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1 Previous work had suggested that adult male click beetles ( Agriotes spp.) show differential responses to species specific pheromone traps. This hypothesis was tested using mark -release -recapture methods to estimate the maximum sampling range and the effective sampling area of traps for three species. 2 Captured beetles of the species Agriotes lineatus , Agriotes obscurus and Agriotes sputator were marked to show the direction of release, the distance of the release point from the trap and the replicate. Analysis of variance showed that there were significant differences in recapture rates between species and release distances. There were no significant differences between release direction and replicates. 3 Calculated linear speeds suggested differences in movement rates in the order:A. lineatus > A. obscurus > A. sputator . There were also substantial differences between the species in the maximum sampling ranges and effective sampling areas of the traps. These placed the species in the same order. 4 The results are used to estimate the minimum cost of mass trapping programmes to prevent males from mating, giving values of € 165/ha/year ( A. lineatus ), € 247.5/ ha/year ( A. obscurus ) and € 2343/ha/year ( A. sputator ). 5 Implications for the use of pheromone traps in wireworm pest management are discussed. It is concluded that current U.K. recommendations based on the cumulative total catch of the three species over a sampling season can be improved by considering the spatial relationships between the adult trapping system and larval distribution. The current constraint to this is the general inability to separate wireworms into species.

Summary 1.Understanding the spatiotemporal ecology of invertebrates in agricultural ecosystems is important for developing management strategies to enhance biodiversity and reduce pesticide use. There is increasing recognition that studies need to be undertaken at scales larger than the field but the ability to do this is often resource limited. Pheromone traps, developed for pest management, can provide a relatively cheap means of collecting data across wide geographical scales. In this study we used such traps to examine the spatial stability of two species of agrioted beetles in non-farmed habitats over a period of 3 years. The spatial distributions of adult male Agriotes lineatus and Agriotes obscuruswere sampled from April until July at a number of sites across 950 ha on Westham Island, British Columbia, Canada. Data were assembled as spatially referenced cumulative trap counts by species and year, and analysed for evidence of aggregation and clustering using spatial analysis by distance indices (SADIE) methodology. Both intraspecific and interspecific association analyses were then carried out. A further set of analyses considered the spatial associations between different sampling dates in 2004. 3. Agriotes lineatus was clustered into patches and gaps at the landscape scale in all 3 years, and A. obscurus showed similar spatial structure in 2002 and 2003. For both species, spatiotemporal stability at the landscape scale was evident. There was also a positive association between the two species in 2 out of the 3 years, suggesting that they were responding in a similar manner to the landscape environment. 4. Synthesis and applications . This study showed that there was substantial temporal stability in the spatial structures of A. lineatus and A. obscurus in non-farmed habitats, and that the two species respond in a broadly similar way to a heterogeneous agricultural landscape. This suggests that models to predict distributions within a landscape could be developed to guide decisions about where to grow vulnerable crops. Identification of the environmental factors that differentiate between clusters and gaps in their spatial distributions may also make it possible to manipulate populations and reduce their impact as pests without recourse to insecticides. Moreover, our results extend the spatial scales over which SADIE statistics have been used, and demonstrate the usefulness of pheromone trapping as a sampling method in addressing ecological questions at a landscape scale.

The soil food web has been referred to as a 'black box', a 'poor man's tropical rainforest' and an 'enigma', due to its opacity, diversity and the limited insight into feeding specificity. Here we investigate the flow of C and N through the soil food web as a way to gain understanding of the feeding interactions occurring. A bacterium, Pseudomonas lurida, was introduced to soil cores from two different habitats, a grassland and a woodland with the same soil type, enriched to 99 atom% in (13)C and (15)N, to trace the flow of bacterial C and N through the soil food web. Throughout the experiment the soil remained enriched in (13)C and (15)N. Almost all the invertebrates tested gained C and N enrichment indicative of the labelled bacteria, implying that bacterial feeding is a common mechanism within the soil. Only three groups were significantly enriched in both (13)C and (15)N in both habitats. These were Collembola (Entomobryomorpha), Acari (Oribatida), and Nematoda, indicating that these organisms are consuming the most bacteria within both systems. When the invertebrates were grouped into hypothesised trophic levels, those considered secondary decomposers were gaining the most enrichment across all invertebrates tested. This enrichment was also high in the micro-predators within the soil, implying that their main food source was the secondary decomposers, particularly the Collembola. Using an enriched bacterium to track the trophic transfer between organisms within the soil food web is a novel way of empirically showing that interactions are occurring, which normally cannot be seen.

1 The production of new insect pheromones for pest monitoring proceeds at a greater rate than their evaluation, with the consequential possibility of premature introduction. Fundamental to their successful deployment is the determination of a consistent relationship between adult male pheromone trap catches and pest damage. In the present study, adult pheromone traps and larval bait traps were used to examine spatial relationships between two species of Agriotes beetle and wireworms at the field scale. 2 The spatial distributions of adult male Agriotes lineatus and Agriotes obscurus in two fields were determined and compared with the distribution of their larvae. Data were assembled as spatially referenced trap counts, and analysed for evidence of aggregation and clustering using Spatial Analysis by Distance IndicEs (SADIE) methodology. Spatial stabilities of adult populations between sampling dates were tested using association tests. Spatial and quantitative linkages between adult and larval trap catches were also tested. Moreover, a new way of adapting SADIE methodologies is presented for situations where two datasets within an area do not share the same sampling points. 3 There was no significant difference in variance : mean relationships for the two species but there were differences in their spatial distributions, and this is a definitive example of the general argument stating that it is important to consider spatial as well as count data in ecological studies. The spatial distribution of A. lineatus varied between sampling occasions at both sites whereas A. obscurus had consistently significant SADIE indices over time at one site, and adult catches could also be linked to larval distributions and counts. It is proposed that observed differences between the two species can be explained by interference between traps and dissimilar movement rates. There was some evidence of an edge effect at the field boundaries. 4 The distance between pheromone traps is related to the time that elapses before adjacent traps interfere with trap captures and this limits the detection of statistically significant spatial patterns. It is shown that the current practice of adding trap counts for different Agriotes species and treating them as numerically equivalent is insufficiently robust to be recommended at this stage. 5 The implications for the use of sex pheromone traps in wireworm pest management are considered. It is concluded that pheromone traps, as currently used, will not reliably indicate where wireworms occur in a field, and that the complexity of interpreting adult male trap counts limits quantitative predictions of population size.

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