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Although communities of generalist invertebrate predators are known to be capable of suppressing pests, little is known about the long-term population dynamics of individual species of generalist predators and single classes of prey in the field. We present evidence of a dynamic interaction between a generalist insect predator, the carabid beetle Pterostichus melanarius, and its slug prey. We analyzed the numbers of slugs and beetles in an arable field over a 5-yr period, during the main activity period of the beetles from June to September. The field contained 25 plots comprising five replicates of five cultural treatments. An index of the nutritional status of the 8497 beetles collected was obtained by weighing the crop of each beetle (a measure of total prey availability per predator). There was a strong relationship between the crop mass of the beetles and slug numbers in the soil, indicating that slugs were a major part of the diet of the beetles. The change in the beetle population from year to year was strongly related to both slug numbers in the soil and the crop mass of the beetles. This indicated that the slugs influenced the nutritional status, and hence the reproductive success, of the beetles. The predators had a significant effect on slug population growth between years but not between months within years. The temporal effect of these processes was a between-year coupling of beetle and slug population dynamics, buffered by feeding on other prey. The relationship appears to be similar to that between mammalian predators and limited numbers of prey species in the subarctic, where one prey species forms a substantial proportion of the total available food resources. Such relationships may be common in agroecosystems, where species diversity is low, and may be a significant factor driving periodic fluctuations in the abundance of both predators and pests. Key words: agroecosystems; coupled dynamics; density dependence; Deroceras reticulatum; generalist predators; gut mass and nutritional state; Pterostichus melanarius.

Money spiders (Linyphiidae) are an important component of conservation biological control in cereal crops, but they rely on alternative prey when pests are not abundant, such as between cropping cycles. To optimally benefit from these generalist predators, prey choice dynamics must first be understood.Money spiders and their locally available prey were collected from cereal crops 2 weeks pre‐ and post‐harvest. Spider gut DNA was amplified with two novel metabarcoding primer pairs designed for spider dietary analysis, and sequenced.The combined general and spider‐exclusion primers successfully identified prey from 15 families in the guts of the 46 linyphiid spiders screened, whilst avoiding amplification of Erigone spp. The primers show promise for application to the diets of other spider families such as Agelenidae and Pholcidae.Distinct invertebrate communities were identified pre‐ and post‐harvest, and changes in spider diet and, to a lesser extent, prey choice reflected this. Spiders were found to consume one another more than expected, indicating their propensity towards intraguild predation, but also consumed common pest families.Changes in spider prey choice may redress prey community changes to maintain a consistent dietary intake. Consistent provision of alternative prey via permanent refugia should be considered to sustain effective conservation biocontrol. [ABSTRACT FROM AUTHOR]

Many Lepidoptera larvae use pieces of vegetation bound with silk to construct or disguise their cocoons. Here we report the first known case of a caterpillar building its cocoon entirely out of fragments of resin, broken away from sheets of dried resin on the trunk of a tree and held together with silk. The behaviour of the larva (possiblyNegritothripasp. in the Nolidae), from the Kinabatangan Wildlife Sanctuary in Sabah, Borneo, is described. The cocoon was constructed on the trunk ofVatica rassak(Dipterocarpaceae). Analysis of resin from the cocoon, using gas chromatography-mass spectrometry, revealed a complex mixture of 260 components, dominated by sesquiterpenes and triterpenes. Many of these compounds have defensive properties, protecting the tree from herbivores and fungi. The larva appears to have evolved an elaborate and possibly unique behaviour, allowing it to harness the defensive properties of the resin to protect its pupa from predators and/or entomopathogenic fungi. [ABSTRACT FROM AUTHOR]

Predatory carabid beetles are important for regulating prey abundance in terrestrial ecosystems. While surveys of carabid diet have revealed many insights into trophic interactions, the high species diversity and heterogeneous developmental stages of prey identified in the gut have made further advances difficult. In addition, the carabid gut contains partially digested and mainly soft tissue parts of the prey species, difficult to identify by traditional methods. Molecular gut content analysis (MGCA) avoids these disadvantages but to date has been limited primarily to revealing pest species in agricultural fields. Here we used MGCA to screen for the presence of Lepidoptera in carabid guts, in woodland ecosystems, in both Croatia and the UK. Data on carabids positive for Lepidoptera were compared with those from previous work on the same carabid assemblages, screened for earthworms, slugs, woodlice and springtails. In both locations, the prey group most frequently detected was earthworms, followed by slugs and Lepidoptera and then finally by woodlice and springtails. The composition of the diet changed with season, carabid sex, and carabid size. In both locations, Lepidoptera were the third most frequent prey, with 27% of carabids testing positive in Croatia and 20% in UK, suggesting that carabids could be significant predators of Lepidoptera in woodland ecosystems and may potentially play an important role in controlling moth pests. [ABSTRACT FROM AUTHOR]