Brown recluse spider bites often go unnoticed initially because they are usually painless bites. Occasionally, some minor burning that feels like a bee is noticed at the time of the bite. Symptoms usually develop 2-8 hours after a bite. Keep in mind that most bites cause little tissue destruction.
Initially the bite site is mildly red and upon close inspection may reveal fang marks. Within a few hours, the redness gives way to pallor with a red ring surrounding the area, or a "bull's-eye" appearance. The lesion will often appear to flow downhill over the course of many hours. The center area will then often blister, which over 12-48 hours can sink, turning bluish then black as this area of tissue dies. Read more about the treatments for brown recluse spider bites.
Article: Brown Recluse Bite Treatment