What are black widow bites like? Do they turn necrotic like brown recluse bites?
No, black widow spider venom is a neurotoxin.
I found this:
What are the symptoms of a bite?
A black widow spider bite gives the appearance of a target, with a pale area surrounded by a red ring. Severe muscle pain and cramps may develop in the first two hours. Severe cramps are usually first felt in the back, shoulders, abdomen and thighs. Other symptoms include weakness, sweating, headache, anxiety, itching, nausea, vomiting, difficult breathing and increased blood pressure. Young children, the elderly and those with high blood pressure are at highest risk of developing symptoms from a black widow spider bite.