Spiders play a vital role in agricultural ecosystems by capturing and preying on small insects, thereby controlling the pests around crops. However, without directly collecting the specimen, it is challenging to accurately determine the species of the spider that formed the web and its diet. Spiders dissolve their prey with digestive fluids while consuming; thus, leaving very little residue in their digestive system. This study aimed to identify the spider that formed the web and the prey caught in the web using environmental DNA (eDNA) present in the spider web. For this purpose, eDNA using the mitochondrial cytochrome C oxidase subunit I (COI) gene was extracted from five adjacent spider webs collected from residences near agricultural environments. Based on the genes extracted from spider webs, it was confirmed that the most commonly found gene in all five spider webs was COI of Parasteatoda tepidariorum, and no other spider genes were detected. Among the five spider webs, prey was found in only one web, and in that web, genes of arthropods other than spiders were detected. The genes of the prey found in the spider web were identified to be those of Orthocladius tamarutilus, Tanytarsus tamagotoi, and Yemma exilis. Thus, without directly collecting arthropod specimens from the spider web, it was possible to identify the spider and its prey. This provides crucial information that can help in clearly understanding the predatory activities of spiders in agricultural ecosystems in the future.

Keywords: Arthropoda, environmental DNA, metabarcoding, spider, spider web