Summary1. The spatial dynamics of farmland invertebrates can provide essential information relevant to their management for pest control and biodiversity conservation in sustainable agriculture. Carabid beetles are one of the most important groups contributing to biological control in arable fields. Previous studies have focused on spatial dynamics within single fields and years. In this study we examined their larger scale, long-term dynamics, thereby taking into account the impact of changes in crop rotation and the influence of field size. 2. The spatial distributions of four beetle species were investigated at an unprecedented spatial scale in a grid of 973 pitfall trap locations across six fields encompassing 64 ha of arable land. Week-long trapping was conducted four times in the first year and twice in the two following years. 3. All species showed strong aggregation but the size and location of patches differed among species. The distribution of Pterostichus melanarius was stable within and between years, with a single large patch close to the field boundaries. Patches of Poecilus cupreus were also located close to field boundaries but their location changed between years. Pterostichus madidus and Philonthus cognatus distributions extended across field boundaries and were less stable, with patch locations changing between years. 4. Synthesis and applications . The spatial extent of a population patch for a given species was species-specific. Species overwintering in field boundaries remained in proximity to these throughout the summer, whereas patches of mid-field overwintering species were more extensive. Patches were generally stable within years but varied for some species between years. Species therefore differ in their response to crop management practices and consequently blanket management approaches for these important generalist predators of crop pests are inappropriate. For spatially stable species (e.g. Pterostichus melanarius ) it may be possible to determine their specific habitat requirements and to devise predictive and protective measures to preserve populations or manipulate them at the farm-scale. More mobile species may be better at responding to pest aggregations at the farm-scale. However, operations that deplete populations, e.g. soil cultivations, should be spatially and temporally desynchronized at the farm-scale to conserve populations and enable functional biocontrol.

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In many European countries agri-environment funding can improve ecosystem services, including the adoption of conservation biocontrol, through the creation of habitats that encourage beneficial arthropods. Predatory beetles are amongst the most numerous and diverse arthropods present in arable fields. The primary ecosystem services provided by predatory beetles are in biological control and food chain maintenance as they are a key resource for many higher organisms. However, to be effective biological control agents, able to respond quickly to wherever a pest infestation occurs, then they must be sufficiently abundant and widely distributed. Conservation biocontrol utilising predatory beetles has focussed on the impact of species that overwinter in adjacent field boundaries, although those overwintering within fields are often more abundant. If the abundance and distribution of predatory beetles is to be maximised then further knowledge of their spatial dynamics is required to ensure habitats are arranged appropriately. The spatio-temporal dynamics of boundary and field overwintering species was measured across 64 ha encompassing six fields and for three consecutive years using a grid of 973 pitfall traps. Boundary species were more numerous in spring (May and June) whereas more field species were captured in July. The species composition was comprised of relatively few taxa. Boundary species occurred in small patches that were distributed across the fields in spring, but were only found close to the margins in July. Patches persisted in some locations over two years. Field species occurred in larger patches, spread across particular fields and these were stable within years and to some extent between years. Game-cover strips were attractive to boundary species in the spring and summer and did not effect predator distribution in the adjacent crop.

Predatory beetles contribute to the control of crop pests and are an important food resource for farmland birds. Many of these beetle species overwinter as larvae within agricultural soils, however, their spatio-temporal emergence patterns are poorly understood, even though such knowledge can assist with their management for biocontrol. Soil moisture is considered to be a key factor influencing oviposition site selection and larval survival. The time, density and spatial pattern of Carabidae and Staphylidae emergence was therefore measured across two fields and compared to soil moisture levels in the previous winter and adult distribution in the previous July. The mean density of Carabidae and Staphylidae that emerged between April and harvest within each field was 157 and 86 m-2, indicating that soils are an important over-wintering habitat for beneficial invertebrates and should be managed sympathetically if numbers are to be increased. Of the species that were sufficiently numerous to allow their spatial pattern to be analysed, all showed a heterogeneous emergence pattern, although patches with high emergence were stable over the sampling period. The distribution of eight species was influenced by soil moisture levels in the previous winter and eight species, although not the same, were spatially associated with the distribution of adults in the previous summer suggesting that the females selected oviposition areas with the appropriate soil wetness.

Invertebrates are an essential food source for most farmland birds yet their relative abundance and biomass in the most commonly grown arable crops are poorly understood. Dvac suction sampling was used to determine the abundance, biomass and community composition of those invertebrate groups considered important in the diet of farmland birds for the commonest arable crops. Approximately 40 fields were sampled at the edge and mid‐field over 2 years in three different locations in England. In cereals, the fauna was primarily comprised of Araneae (10%), Coleoptera (30%) and Hemiptera (58%), whereas the oilseed rape fauna was dominated by Coleoptera (65%) and peas and potatoes by Hemiptera (89%). Beans contained a high proportion of Coleoptera (39%) and Hemiptera (49%). Aphididae were the most abundant family (20–86% of total), although in oilseed rape and beans, Chrysomelidae, Curculionidae and Nitidulidae formed ca 20% of the fauna. Aphids only formed a small proportion (7%) of the total biomass, except in peas (32%). Instead, Araneae, Carabidae, Heteroptera, Homoptera and Tipulidae formed much larger and more equal proportions. The highest abundance and biomass of invertebrates were recorded in cereals and least in potatoes. The Grey Partridge chick‐food index in all crops was only a half or less of the level required to ensure that chick survival is sufficient to maintain numbers of this red‐listed species. The total number of invertebrates, their biomass, diversity and the Grey Partridge chick‐food index were higher at the crop edge compared to mid‐field. Conservation measures are needed to help reverse the long‐term declines of invertebrates on farmland, which should include developing further invertebrate‐rich, agri‐environment scheme options and management techniques to encourage invertebrates considered important as bird food within arable crops.