The high number of rain days this summer lead to a boom in the spider population, who hunted down the stink bugs.
The web of life is such a wonder. Following the first US landing, in Allentown PA, of a successful breeding population of Chinese Stink Bugs, US Mid-Atlantic states were swarming with the damn things (see photo below). The Chinese Stinkers don’t bite but they are large and medieval looking; and, when harassed or squashed they exude a horrid smell.
Homes of rich and poor alike were infested day and night, upstairs and down, for three years running. Then this summer, suddenly, they nearly disappeared from the western suburbs of Philadelphia. I think I know at least one reason why there were fewer Chinese Stink Bugs this year: wolf spiders, like the one pictured above, ate them. Treehugger