Descartes,
They were brown recluses, I still have them to this day. Those pictures are the exceptions.. most bites prove to be minor. It depends on who gets bit and how much venom the spider gets in you.
Black widow spider
Shiny, black, with a red hourglass marking on the abdomen of the female, this arachnid is found in dark corners of sheds, under logs, and in rock piles. Black widows are found in both settled and unsettled areas. The spider will bite, if provoked, and the bite can be dangerous to all ages. It is seldom fatal. However, the pain spreads throughout the body, accompanied by headache, dizziness, nausea, and excruciating cramps. Ice is very helpful and if put on the site immediately, can detoxify the bite. Seek medical attention
Brown recluse spider
Light brown in color and about 1/2 inch in length, these spiders are active at night. The rear end is the widest part, with the center being smaller, and the head being very tiny. The head has a black streak. This spider looks like a small walking violin and is rare in the desert. The bite is usually unnoticed, but it is an ulcerous wound and extremely difficult to heal. Medical assistance may be necessary.
Above found here.
Notice for the Brown recluse it states: bite is usually unnoticed and where it says medical assistance may be necessary.
A black widow bite is 10x more venemous than a rattlesnake.. but a black widow bite barely gets any venom injected.