PERSECUTED AND TOLERATED GUESTS. 



38' 



2. Indifferently Tolerated Guests, or Synoeketes. These live in 

 the nests without being noticed by the ants or without arousing any 

 great animosity, because they are either too small or too slow of move- 

 ment to be perceived, or have no specific odor that differentiates them 

 from their environment, or because the ants are unable to seize and 

 hold them and therefore soon learn to let them alone. 



3. True Guests, Symphiles, or Myrmecoxenes. Species which are 

 amicably treated, i. c., licked, fondled, fed and even reared by the ants. 

 These guests represent the most extreme and remarkable development 

 of myrmecophily. 



4. Ecto- and Entoparasites. Species that live either on or in the 

 ants and present adaptive peculiarities similar to those of the ecto- and 

 entoparasites of other animals. 



The symphiles represent the elite, as Wasmann calls them, of the 

 myrmecophiles, and number hardly more than 300 to 400 species, 

 whereas the synoeketes are much more numer- 

 ous. With the increasing intimacy of the sym- 

 biotic relation as we pass from the first to the 

 fourth of the groups above mentioned, there 

 goes a concomitant increase in the number and 

 magnitude of adaptive characters. The object 

 of the myrmecophiles is to live their own sweet 

 lives unmolested in the midst of the warmth and 

 plenty of the nest. We see, therefore, a gen- 

 eral tendency in many of these creatures to 

 mimic the ants in color, form or pilosity 

 (mimetic type), in others to assume a limuloid 

 shape, with broad shoulders and rapidly taper- 

 ing abdomen, combined with a hard or very 

 slippery surface, which prevents their being 

 held fast by the ants (loricate type), and in 

 others to develop tufts of yellow, scent-diffus- 

 ing hairs, which appeal to the gustatory and 

 olfactory senses of the ants ( symphiloid type). 

 The mimetic and loricate types are most per- 

 fectly realized among certain synechthrans and 

 symeketes, whereas the symphiloid characters, though foreshadowed in 

 some of these insects, reach their full development only in the^rue 

 guests. The parasites of ants, finally, like those of other animals, have 

 acquired the most exquisite and specialized apparatus for exploiting 

 the individual host. I shall here consider a number of typical synech- 



FIG. 226. Megasti- 

 licus formicaritts, a syn- 

 echthran from the nests 

 of Formica e.vsectoides. 

 (Original. ) 



