UNFORTUNATELY, the various captions that have accompanied these viral images over time haven't included enough information to confirm whether the wound depicted in them resulted from the bite of a brown recluse ("fiddleback") spider or some other cause. The origin of the images remains unknown.
The wound itself looks real enough regardless of what caused it, and the lesions do resemble necrotic ulcers symptomatic of brown recluse spider bites. They're also symptomatic of gangrene and necrotizing fasciitis, however, both of which can result from a brown recluse bite but have other known causes as well, and can easily be mistaken for such a bite. Experts say misdiagnoses of the causes of necrotic ulcers are quite common.
Unlike the example in the preceding photos, the majority of brown recluse bites are "uneventful," doctors say, and rarely progress to such a serious stage.
Sources and further reading:
Brown Recluse Bite Symptoms
University of Nebraska Dept. of Entomology
Brown Recluse Spider
A.D.A.M. Healthcare Encyclopedia
Brown Recluse Spider Bite on the Hand (Image)
A.D.A.M. Healthcare Center
Factsheet: Brown Recluse Spider
Ohio State University
Convenient Culprit: Myths Surround Brown Recluse Spider
American Medical News, 5 August 2002
Myth of the Brown Recluse
By Rick Vetter, U.C. Riverside Dept. of Entomology
Last updated: 03/14/12