Predatory natural enemies play key functional roles in biological control. Abundant predatory arthropod species have been recorded in tea plantation ecosystems. However, few studies have comprehensively evaluated the control effect of predatory arthropods on tea pests in the field. We performed a one-year field investigation and collected predatory arthropods and pests in the tea canopy. Total 7,931 predatory arthropod individuals were collected, and Coleosoma blandum (Araneae, Theridiidae) was the most abundant species in the studied tea plantation. The population dynamics between C. blandum and four main tea pest species (Aleurocanthus spiniferus, Empoasca onukii, Ectropis grisescens and Scopula subpunctaria) were established using the individual number of predators and pests in each month. The results showed that the occurrence of C. blandum showed high synchronism with the occurrence of A. spiniferus, Em. onukii and Ec. grisescens. The prey spectrum of C. blandum was further analyzed using DNA metabarcoding. Among prey species, A. spiniferus, Em. onukii and Ec. grisescens were included, and the relative abundance and positive rates of target DNA fragments of A. spiniferus were obviously greater than those of other two pests.

Spiders are the most dominant predatory natural enemies of insect pests in the tea plantation ecosystem. There has been a large amount of literature published about the investigation of spider species in Chinese tea plantations from 1982 to 2020. Here, the spider species in Chinese tea plantations has been summarised and the dominant spider species in each regional tea plantation recorded. To date, there were 535 spider species from 40 families reported in Chinese tea plantations, with a total of 13 families and 245 species now being added. A total of 89 spider species from 19 families were the dominant species, amongst them, Agelena labyrinthica, Allagelena difficilis, Neoscona theisi, Clubiona deletrix, Clubiona japonicola, Hylyphantes graminicola, Pardosa laura, Oxyopes sertatus, Evarcha albaria, Plexippus paykulli, Coleosoma octomaculatum, Ebrechtella tricuspidata and Xysticus ephippiatus were recorded in many tea plantations. The checklist will provide important data for the biodiversity and distribution of spiders in tea plantations of China.

Studies of predation can contribute greatly to understanding predator-prey relationships and can also provide integral knowledge concerning food webs and multi-trophic level interactions. Both conventional polymerase chain reaction (cPCR) and quantitative PCR (qPCR) have been employed to detect predation in the field because of their sensitivity and reproducibility. However, to date, few studies have been used to comprehensively demonstrate which method is more sensitive and reproducible in studies of predation. We used a Drosophila melanogaster-specific DNA fragment (99 bp) to construct a tenfold gradient dilution of standards. Additionally, we obtained DNA samples from Pardosa pseudoannulata individuals that fed on D. melanogaster at various time since feeding. Finally, we compared the sensitivity and reproducibility between cPCR and qPCR assays for detecting DNA samples from feeding trials and standards. The results showed that the cPCR and qPCR assay could detect as few as 1.62×103 and 1.62×101 copies of the target DNA fragment, respectively. The cPCR assay could detect as few as 48 h post-feeding of the target DNA fragment. But the qPCR assay showed that all spiders were positive after consuming prey at various time intervals (0, 24, 48, 72 and 96 h). A smaller proportion of the technical replicates were positive using cPCR and some bands on the agarose gel were absent or grey, while some were white and bright for the same DNA samples after amplification by cPCR. By contrast, a larger proportion of the technical replicates were positive using qPCR and the coefficients of variation of the Ct value for the three technical replicates of each DNA sample were less than 5%. These data showed that qPCR was more sensitive and highly reproducible in detecting such degraded DNA from predator’s gut. The present study provides an example of the use of cPCR and qPCR to detect the target DNA fragment of prey remains in predator’s gut.

As one of the most abundant predators of insects in terrestrial ecosystems, spiders have long received much attention from agricultural scientists and ecologists. Do spiders have a certain controlling effect on the main insect pests of concern in farmland ecosystems? Answering this question requires us to fully understand the prey spectrum and prey preferences of spiders in the farmland ecosystem of concern. Next-generation sequencing (NGS) has been successfully employed to analyze spider prey spectra by sequencing prey DNA barcode regions and matching the sequence results to DNA barcodes from public databases. However, considering the high cost of this technology, we performed a comparative analysis of the prey spectra of Ovia alboannulata (Araneae, Lycosidae) (a dominant spider species on Chinese tea plantations) using NGS with individual and mixed DNA samples to demonstrate which treatment was better for determining the spider’s prey spectrum in the field. We collected spider individuals from tea plantations. Two treatments were then used to analyze the spider’s prey spectrum: (1) the DNA was extracted from the spiders individually and then sequenced separately and (2) the DNA was extracted from the spiders individually and then mixed and sequenced.