No facts, only a guess about the cause.

To derterrents, add inquisitive children who collect bugs in bottles, etc. They cut down on insect and spider populations.

I remember a "plague" (read common) of black widow spiders. They seemed to like old woodpiles, garage corners, and the like. Along with my grade school mates, we caught a good many and displayed them in jars.

Our teachers (about grade five) taught us how to prepare and mount insects in collections. I know this and similar projects nurtured my interest in science and determined my life work.