Invasive brown widow spiders avoid parasitism despite high densities.

Invasive species are sometimes less susceptible to natural enemies compared to native species, but the mechanism is often unclear. Here we tested two potential mechanisms for lower parasitism of invasive species: density-dependent parasitism and preference for human-dominated habitats. We investigated how variation in host density and habitat type affect egg sac parasitism in two widow spider species (family Theridiidae). We compared parasitism on the egg sac of the brown widow, Latrodectus geometricus, an urban invasive species, and the white widow, Latrodectus pallidus, a species native to Israel. To investigate variation in host and parasitoid density, we measured nearest-neighbor distance between spider webs and parasitism rates in 16 sites, and in a single site monthly throughout a year. In L. pallidus, denser sites were more heavily parasitized (up to 55%) and parasitism rate increased with population density throughout the season. Extremely dense L. geometricus populations, however, had very low rates of parasitism (0-5%). We then conducted an egg sac transplant experiment in human-dominated and natural habitats. We found no parasitism of either species in the human-dominated habitat, compared to 30% parasitism of both species in the natural habitat. In addition, we found evidence for higher predation of L. pallidus than of L. geometricus egg sacs, particularly in the natural habitat. These combined results suggest that the human-dominated habitats inhabited by L. geometricus have a lower abundance of predators and parasites. We conclude that lower parasitism and predation in human-dominated habitats could contribute to the invasion success of L. geometricus.

The global spread of misinformation on spiders.

In the internet era, the digital architecture that keeps us connected and informed may also amplify the spread of misinformation. This problem is gaining global attention, as evidence accumulates that misinformation may interfere with democratic processes and undermine collective responses to environmental and health crises1,2. In an increasingly polluted information ecosystem, understanding the factors underlying the generation and spread of misinformation is becoming a pressing scientific and societal challenge3. Here, we studied the global spread of (mis-)information on spiders using a high-resolution global database of online newspaper articles on spider-human interactions, covering stories of spider-human encounters and biting events published from 2010-20204. We found that 47% of articles contained errors and 43% were sensationalist. Moreover, we show that the flow of spider-related news occurs within a highly interconnected global network and provide evidence that sensationalism is a key factor underlying the spread of misinformation.

An expert-curated global database of online newspaper articles on spiders and spider bites.

Mass media plays an important role in the construction and circulation of risk perception associated with animals. Widely feared groups such as spiders frequently end up in the spotlight of traditional and social media. We compiled an expert-curated global database on the online newspaper coverage of human-spider encounters over the past ten years (2010-2020). This database includes information about the location of each human-spider encounter reported in the news article and a quantitative characterisation of the content-location, presence of photographs of spiders and bites, number and type of errors, consultation of experts, and a subjective assessment of sensationalism. In total, we collected 5348 unique news articles from 81 countries in 40 languages. The database refers to 211 identified and unidentified spider species and 2644 unique human-spider encounters (1121 bites and 147 as deadly bites). To facilitate data reuse, we explain the main caveats that need to be made when analysing this database and discuss research ideas and questions that can be explored with it.