ARTHROPODA 



309 



Fig. 151. 



Pig. 151. Spiders (,Epeira marmorea). After McCook. Male on left; female on right. Natural 



size. 



Questions on the figure. — What differences do you note with respect to the 

 sexes? What habits of the spiders are correlated with this difference in size in the 

 sexes? 



Fig. 152. 



Fig. 152. Web of Epeira slrix, an Orb-weaving Spider. After McCook. 



Questions on the figure. — By reference to other texts or by observation 

 determine if there is any regular order in which the parts of the web are produced. 

 To what is this form of web an adaptation? Evidences? What other forms of 

 webs are constructed for similar purposes? 



