A nocturnal hunter, the Yellow Sac spider rests in a sac during the day. This spider is a particularly hazardous pest due to its tendency to bite humans. Yellow Sac spiders account for the majority of spider bites in humans. These bites are not particularly dangerous, but they do produce large, red sores followed by white pustules. Don’t hesitate to call AAA Exterminating to rid your home of this troublesome pest.