<unk>  violin shape on cephalothorax (fiddleback)
In Southern midwestern US
Loxosceles family
Venom contains variety of cytotoxic enzymes, principally Hyaluronidase and Sphingomyelinase-D, which cause a necrotic wound
Hyaluronidase: facilitates the penetration of the venom into tissue but does not induce lesion development
Sphingomyelinase-D:  causes necrosis and lesion formation by initiating the release of pro-inflammatory mediators (thromboxanes, leukotrienes, prostaglandins, and neutrophils)
Hyaluronidase: facilitates the penetration of the venom into tissue but does not induce lesion development
Sphingomyelinase-D:  causes necrosis and lesion formation by initiating the release of pro-inflammatory mediators (thromboxanes, leukotrienes, prostaglandins, and neutrophils)
Brown recluse spider bite
Hymenoptera stings 
Armed spider bite
Mammalian bites
Octopus bite
Closed fist infection 
Funnel-web spider bite
Dog bite