Black Widow Spiders - DesertUSA: "Caution - Venomous!
The venom of the female black widow spider is 15 times as toxic as the venom of the Prairie Rattlesnake. Only a minute amount of the toxin is injected in a single bite by the spider however, so they are rarely fatal. By comparison, the relatively large amount of injected rattlesnake venom results in about 15 to 25 percent mortality among those bitten.
The bite itself is often not painful and may go unnoticed. But the poison injected by the the Black Widow bite can cause abdominal pain similar to appendicitis as well as pain to muscles or the soles of the feet. Other symptoms include alternating salivation and dry-mouth, paralysis of the diaphragm, profuse sweating and swollen eyelids.
Persons with heart conditions or other health problems may require a hospital stay. (Heart and lung failure may result in death.) A physician can evaluate the severity of the bite, and give specific antivenin or calcium gluconate to relieve pain if necessary. Healthy people recover rapidly in two to five days.
First aid measures: Apply an ice pack over the bite location and keep the affected limb elevated to about heart level. Try to collect the spider specimen in a small jar or plastic bag for examination by a spider expert, even if you have crushed it. Treatment in a medical facility may be necessary. Call the Poison Center for additional information. Poison Centers across the country now have a new national emergency phone number - 1-800-222-1222"