SCORPIONS, SPIDERS, MITES AND TICKS 207 



like palpi, are sometimes one-fourth to one-half as long as the 

 legs. The mandibles, or chela, are large and terminate in a 

 slender sharp-pointed fang, through which poison flows when 

 a spider bites its prey. The bite usually quickly kills insects 

 and other small animals but as a rule does not seriously affect 

 A few species, however, are very venomous, and a bite 



man. 



from one of them may result in great suffering, rarely in 



FIG. 94. Web of an orb-weaver, Zilla californica; the viscid threads are 

 omitted from part of the web; a trap-line runs from the center to a retreat 

 at one side. (Much reduced.) 



death. The effect of a spider's bite does not depend altogether 

 upon the kind of spider, the condition of the victim's blood 

 being a considerable factor. Two people may be bitten by the 

 same kind of spider and one suffer little while the effect on the 

 other may be very serious. The most common of the very 

 poisonous spiders, and the only one to be much feared in this 

 country, is the "hour-glass" spider, or "black widow" 

 Latrodectes mactans. This is a small-sized sooty black 



