102 PECKHAM. [Vol. 1, 



animals (or the groups) which resemble each other inhabit the 

 same country, the same district, and in most cases are to be 

 found together on the very same spot. 



2. These resemblances are not indiscriminate, but are 

 limited to certain groups, which, in every case, are abundant 

 in species and individuals, and can often be ascertained to have 

 some special protection. 



3. The species which resemble or "mimic" these dominant 

 groups, are comparatively less abundant in individuals, and are 

 often very rare.* 



The second and third of these laws are confirmed by what 

 we know of mimetic resemblances among spiders. They 

 mimic ants much oftener tlian other creatures, and ants are 

 very abundant, are specially protected, and are much more 

 numerous than the mimetic spiders. To the first law, also, 

 they conform to a great extent, since everything tends to show 

 that in tropical America and in Africa the ant and the spider, 

 the one mimicked and the other mimicking, are always found 

 together. So far as I can discover, however, the ant-like 

 spiders of North America, are not found in company with any 

 species of ant which they resemble. This may be because they 

 do not mimic any particular species, but only the general ant- 

 like form; or, considering that the genera which contain their 

 nearest relatives are much more abundant in Central and 

 South America, it may be that these forms were originally 

 tropical, mimicking some tropical species of ants, and that after 

 the Glacial Epoch they migrated northward, leaving the ants 

 behind them. However this may be, their peculiar form has 

 served them well, since they have maintained themselves as 

 fairly abundant species with a lower fecundity than is found in 

 any other group of spiders. 



The cases in which one species mimics another may be 

 divided, according to the kind of benefit derived, into four 

 classes: Class 1. As a rule, where we find one species mimick- 

 ing another, the mimicked species possesses some special means 



*Natural SHevtion, p. 76. 



