[wmblaettler]

Could this decoy be used in the mating ritual to attract females rather than something to do with predators? From my limited reading, many spiders have rather elaborate mating rituals. Also with females being larger and usually killing the smaller male spiders, having a decoy to distract the female might allow the spider to stay alive longer and mate with more female spiders.

[takluyver]

I think it's the male that goes to the female in such cases. The decoy could perhaps be used to attract males. But I'm not an arachnologist, so there may be some obvious reason why that's not the case.