Lampona spp. do NOT cause necrotizing arachnidism!
Its a myth to the best of my knowledge of arachnid venom compositions, which is fairly decent and up to date. Their bites do not appear to cause the same sort of slow-healing, fleshrotting necrotic ulcerations that Loxosceles spp (violin spiders, recluses) or their deadly brethren, Sicarius spp. (which apparently possess a bite that is at least equal to that of a puff adder, if not more so. Shocking, coming from a spider, given the quantity of venom they can deliver; and especially so given that the genus Sicarius, are araneomorph spiders, which lack the massive, well-developed chelicerae and whopping great venom glands possessed by mygalomorph spiders such as the funnelwebs. The venom potency must be extreme. And may well be, in the case of a couple of species within the genus, the worlds deadliest of all spiders. Bites are extremely rare though, given their isolated habitat, but there is no antivenom available. Of the two cases I have read of, involving bites by a Sicarius spp. spider, one victim lost his arm, the other died of massive disseminated intravascular coagulation within hours.
Similar venom to the recluses, containing sphingomyelinase-D, the necrotic toxin found in recluses (recleese? reclusii? recleeses?
), which is only found otherwise in a few of those strains of pathogenic bacteria that rot flesh, such as those responsible for causing necrotizing fasciitis, the aptly-named 'flesh eating disease', for which certain strains of type-A streptococci are responsible, and is so damned virulent, that it can spread inches within hours, and kill in a day. The only treatment for that is highly aggressive antibiotic therapy, combined with similarly very aggressive cutting out of both the diseased area, and a fair margin of healthy tissue around the infection.
Antibiotics aren't going to help with a bite from one of thees spiders though, and they are much larger than a recluse, and can inject far, far, FAR more massive quantities of venom. More to the point, the venom itself can contain, IIRC, several orders of magnitude more sphingomyelinase-D than can even the most venomous of the recluse family (Loxosceles laeta, the chilean recluse, if I remember my arachnid toxicology correctly)
http://www.ncbi.nlm.nih.gov/pubmed/12914510This study examined over a hundred confirmed bites by Lampona spp. (the genus to which the white-tailed spiders belong) and found NO evidence of necrotizing effects like recluse bites produce. The venom is however, known to contain proteases, but as far as I am aware, does not contain sphingomyelinase-D. IIRC the main protease components are hyaluronidases. If white-tailed spiders do pack sphingomyelinase-D, then they must not produce and/or deliver very much of it.
Apparently they can produce slow-healing wounds, but they do not become necrotic like recluse spider or viper bites do.
phobia.