When I was a kid, many years ago, August and September would be the month my parents’ back yard was filled with big orb webs. These webs would have a whitish zig-zag pattern in the middle, and would be occupied by large yellow and black spiders that sat with four legs swept way forward and four legs swept backwards. Looking them up today, they were almost certainly Argiope aurantia (black and yellow garden spider).

Today, my mother’s garden is still host to many orb weavers, but primarily the squatter, orange-brown Araneus diadematus (European garden spider). There haven’t been any of the black and yellow spiders in the garden for years.

Similarly, when I moved into my in West Los Angeles, we would have several Peucetia viridans (green lynx spider) every autumn among the coneflowers, where they would guard a giant egg sac that would hatch out hundreds. We haven’t seen a green lynx spider in the garden for over a decade.

So what’s happened? Have these species been out-competed by the influx of other species? Araneus diadematus are now common in both places, as are Latrodectus geometricus (brown widow spider), neither of which were common before (at least as far as I can remember). Or is it a change in microclimate? Our winters haven’t been getting as cold, and our summers are longer in both places.

It’s strange being old enough to notice systemic change in an environment. In the grand scheme of things, fifty years isn’t that long. But in that timeframe, atmospheric CO₂ levels have gone up by over 100PPM, and somewhere around 85% of all plastics ever produced have been made. Smog levels in the LA Basin have decreased (or at least changed: lead levels are way down, ozone levels are way down, microparticulates are up). These changes may be completely unrelated to the spider situation, though.