PROTECTIVE AND AGGRESSIVE MIMICRY 255 



more and more mimetic, and, on the other (that of 

 their enemies), more and more able to penetrate 

 through the assumed disguises.' l This argument is 

 of course equally applicable to the wonderful cases 

 of Protective Resemblance for the sake of conceal- 

 ment. 



Insects mimicked by animals belonging to a 

 different class 



We must now pass on to cases in which there is a 

 still wider interval between the mimicker and the 

 species which shelters it from attack. The Insecta 

 form one important class of the sub-kingdom Arthro- 

 poda, while the Arachnida (including the spiders and 

 scorpions) constitute another of its classes. Very 

 important anatomical differences separate these two 

 classes, and yet members of the latter are known to 

 mimic species belonging to the former. Thus, spiders 

 which mimic ants are known in both the Old and the 

 New World. One such mimetic spider was believed by 

 Mr. Belt to be an ant until he had killed it. The 

 antennae of the ant were represented by the two fore 

 legs of the spider, and they were held and moved 

 about in the characteristic manner. This resemblance 

 has been explained as Aggressive rather than Protec- 

 tive Mimicry, enabling the spiders to approach the 

 ants upon which they are supposed to prey. Mr. Belt, 

 however, points out that the ants, being free from 



1 Loc. cit. pp. 383, 384. 



