242 AMERICAN SPIDERS 



dously enlarged. One of the largest American wolf spiders has 

 glands proportionately much smaller than those in the black widow 

 and in many lesser spiders. The strongly built vagrants have a supe- 

 rior physical equipment, with more powerful chelicerae and stouter 

 legs to control their prey, and may get along very well with a 

 lesser amount of venom. On the other hand, more delicate spiders 

 have the problem of subduing large, often dangerous insects, and 

 in some cases may compensate for their deficiencies by producing 

 a greater or more potent amount of venom. While there is no 

 evidence to show that the quantity and virulence of the poison are 

 correlated with physique or other factors, it is clear that spider 

 venoms vary markedly, and produce different effects. 



Spider poisons are classified on the basis of their action on man 

 and other warm-blooded animals. Unfortunately, the various chemi- 

 cal compositions are largely unknown and the various toxins still 

 unidentified. They seem to be much more complex than those of 

 other arachnids, and produce symptoms showing the presence of 

 neurotoxins and hematoxins, both of which are sometimes present 

 in the same venom. 



The great majority of spiders, and almost all those from the 

 United States and other temperate areas, have a venom so feeble 

 that its transitory effects are insignificant. In most instances, the 

 bite is followed by local symptoms at the site of the punctures- 

 burning, throbbing, and similar painful sensations, numbness, stiff- 

 ness, and sometimes a very slight swelling. These symptoms usually 

 persist for only a matter of minutes, or a few hours at most, then 

 disappear entirely which indicates that the action is largely a local, 

 mechanical one, and that the venom itself lacks harmful toxins. The 

 severity of this type of injury usually does not exceed the sting of 

 a wasp; only those individuals inordinately susceptible to the ven- 

 oms of arthropods are affected in any important way. 



The poisons of a few spiders, however, are fortified with toxins 

 that cause severe local or general reactions. Some contain hema- 

 toxins that destroy the cells in the vicinty of the wound until large 

 areas of cutaneous tissue are sloughed off, exposing underlying 

 muscles and organs. Such a progressive necrosis, often resulting in 

 gangrene, is caused by several South American species, notably the 

 wolf spider, Lycosa raptoria, of Brazil. Similar grave symptoms are 

 attributed to a mysterious and still unknown Argentine spider of 

 small size, dubbed "arana homicida" which is charged with most 

 of the deaths from spider bite in that country. It has been thought 



