The Jorō spider (Trichonephila clavata) in the southeastern U.S.: an opportunity for research and a call for reasonable journalism

Explosive Growth of the Jorō Spider (Trichonephila clavata (L. Koch): Araneae: Araneidae) and Concurrent Decline of Native Orbweaving Spiders in Atlanta, Georgia Forests at the Forefront of the Jorō Spider's Invasive Spread

The Jorō spider (Trichonephila clavata (L. Koch): Araneae: Araneidae), an invasive species from Asia, and native orbweaving spiders were censused at 25 forest sites in the Atlanta, Georgia, region at the forefront of the Jorō spider's spread from 2022 through 2024. The Jorō spider was found in all 25 sites in all three years, doubling in abundance each year. In 2022, the number of Jorō spiders found was 444 or 16.34 per hour of census. This doubled in 2023 to 859 or 30.54 per hour. The Jorō numbers doubled again in 2024 to 1713 or 59.14 per hour. This contrasts markedly with the seven species of native orbweavers found during the censuses, which declined by ca. 40% each year. In 2022, 52 or 1.72 individuals per hour of six native orbweaver species were found at 18 sites. In 2023, the number dropped to 32 or 1.06 individuals per hour of six species found at 11 sites. In 2024, the number further declined to 18 or 0.55 individuals of six species found at eight sites. The Jorō spider's spread and rapid increase in abundance may disrupt trophic networks and negatively influence the abundance of both native orbweavers and flying insect species.

Honey, What's for Dinner? Dietary Overlap and Size Dimorphism Between Female and Male Joro Spiders (Trichonephila clavata)

Selection on body size tends to favor larger males that outcompete smaller males to mate with females, and larger, more fecund females. For many web-building spiders in the Nephilidae family, reproductive success increases with body size, which in turn, is related to diet. The diet of female spiders may overlap with males who share her web, but diet patterns could depend on size if certain males have better access to prey ensnared in the web. Therefore, we tested the hypothesis that Joro spider (Trichonephila clavata) dietary patterns are sex-specific and related to body size and condition. We combined morphometric size analysis with molecular gut content analysis via DNA metabarcoding and high-throughput sequencing to characterize male and female Joro spider diets from 60 webs at 25 locations. Female Joro spiders were larger than males and their diets were more diverse. While male Joro spiders consumed the same prey taxa as females, more than 50 additional taxa were detected in female diets, which led to significant dissimilarity in prey composition between sexes. As male body size increased, diet diversity and body condition decreased, suggesting a potential trade-off between time spent foraging versus active defense of their position on the web. Female and male spiders captured from the same web shared prey taxa. However, the proportion of prey overlap was not related to male size. Combined, Joro spiders show sex-specific dietary patterns, and males appear to have less access to the diverse food captured in female webs.

Catching invasives with curiosity: the importance of passive biosecurity surveillance systems for invasive forest pest detection

First detections of nonnative insect species are often made by curious members of the public rather than by specialists or trained professionals. Passive surveillance is a crucial component of national biosecurity surveillance, highlighted by early detection case studies of several prominent nonnative arthropod pests (e.g., Asian longhorned beetle [ALB], Jorō spider, spotted lanternfly). These examples demonstrate that curiosity and the recognition of novelty in the natural world, along with enabling technology and systems, are a critical part of early detection and effective invasive species management. This is particularly impactful when dealing with conspicuous pests or for new and emerging nonnative species that have yet to be detected in a new location. Data from historical and recent accounts of first detections of ALB incursions and other invasive forest pests underscore the need to invest in passive surveillance reporting systems and fully integrate public observations into existing surveillance frameworks. New automated approaches streamline the assessment of public observations and can generate pest alerts to initiate a formal regulatory assessment. Biodiversity monitoring platforms, such as iNaturalist, provide a focal point for community engagement and aggregate verified public observations. Empowering proactive reporting of biological novelty provides needed support for early detection of invasive species. Embracing the public as active members of the surveillance community can be cost effective and lead to the greatest gains in the proactive management of invasive species around the world.

Do Invasive Jorō Spiders (Trichonephila clavata) from Asia Avoid Eating Unpalatable Monarch Butterflies (Danaus plexippus) in North America?

An invasive spider from East Asia has established in the U.S. southeast (the "jorō spider," Trichonephila clavata) and is rapidly expanding its range. Studies assessing the impact of this species are needed, including how expansive its diet is. An open question is whether monarch butterflies, Danaus plexippus, are a potential prey item for this spider, given that jorō spiders do not coexist with monarchs in their native range. Since monarch larvae feed on milkweed, they sequester cardiac glycosides into their adult tissues, rendering them unpalatable to many predators. At sites within northeast Georgia, we staged a series of trials (n = 61) where we tossed monarchs into jorō spider webs and, for comparison, performed similar trials with another aposematic species, gulf fritillary (Agraulis vanilla), and a palatable species, tiger swallowtail (Papilio glaucus). We recorded the outcome of the trials, which included whether the spider attacked or did not attack the prey. We also conducted a visual survey during the same fall season to look for evidence of jorō spiders consuming monarchs naturally. Our findings revealed that jorō spiders avoided eating monarchs; spiders only attacked monarchs 20% of the time, which was significantly less than the attack rates of similarly sized or larger butterflies: 86% for gulf fritillaries and 58% for tiger swallowtails. Some jorō spiders even removed monarchs from their webs. From our visual surveys of the surrounding area, we found no evidence of natural monarch consumption and, in general, butterflies made up only a fraction of the jorō spider diet. We conclude that jorō spiders appear to recognize monarch butterflies as being unpalatable, even without having a prior history with the species. This invokes questions about how these spiders can immediately recognize their unpalatability without touching the butterflies.

Fine structural characteristics of the chorionic microspheres on the egg surface of the orb web spider Trichonephila clavata

The eggs laid by the orb web spider Trichonephila clavata must overwinter in bitterly freezing and dry conditions before hatching, but there does not seem to be any protection like a compact silk case covering the entire eggmass. Instead, the surface of the eggmass is completely coated with a milky coating called chorionic microspheres (CM). Therefore, we investigated the fine structural characteristics of CM to demonstrate their ecological importance. Although the diameter of CM in outer eggmass exhibits a significant variation, the chorionic surface is coated with a single layer of CM, characterized by a consistent diameter of approximately 2.3 µm. The surface structure of aggregated CM shows short papillary projections demonstrating segmental adhesion of mucous components. CM is insoluble in water but partially soluble in anhydrous ethanol, and its spherical structure is completely decomposed by hexafluoroisopropanol (HFIP), a strong organic solvent. Since our fine structural observations clearly show that CM is not derived from vitellogenic or choriogenetic processes, the CM adhesive coatings during ovipositional process appears to be equivalent to cocoon silk for various protective functions in silken eggcase.