Farewell old friend?

Last year when I was considering which spider species to use a a benchmark for spider recording, I was surprised that the familiar (and easily identified) Garden Spider, Araneus diadematus, was not the best choice (see: Benchmarking Spider Recording, and: Spider Recording in Leicestershire and Rutland). Instead, the money spider Tenuiphantes tenuis was the best fit. While this may be a quirk of the data, it seems that like the familiar House Sparrow, our old friend the facefull-of-spiderweb Araneus diadematus could be on the way out:

"The drastic decline in the abundance of the orb-weaving spider Araneus diadematus over the past half-century documented in this study (Table 1) apparently reveals a bottom-up trophic cascade in response to the widespread insect losses that have occurred across large parts of Europe in recent decades."



Where Have All the Spiders Gone? Observations of a Dramatic Population Density Decline in the Once Very Abundant Garden Spider, Araneus diadematus (Araneae: Araneidae), in the Swiss Midland. https://www.mdpi.com/2075-4450/11/4/248/htm
Aerial web-spinning spiders (including large orb-weavers), as a group, depend almost entirely on flying insects as a food source. The recent widespread loss of flying insects across large parts of western Europe, in terms of both diversity and biomass, can therefore be anticipated to have a drastic negative impact on the survival and abundance of this type of spider. To test the putative importance of such a hitherto neglected trophic cascade, a survey of population densities of the European garden spider Araneus diadematus—a large orb-weaving species—was conducted in the late summer of 2019 at twenty sites in the Swiss midland. The data from this survey were compared with published population densities for this species from the previous century. The study verified the above-mentioned hypothesis that this spider’s present-day overall mean population density has declined alarmingly to densities much lower than can be expected from normal population fluctuations (0.7% of the historical values). Review of other available records suggested that this pattern is widespread and not restricted to this region. In conclusion, the decline of this once so abundant spider in the Swiss midland is evidently revealing a bottom-up trophic cascade in response to the widespread loss of flying insect prey in recent decades.