78 Chapter II. 



automatically a certain, fixed species of slaves. In 

 May, 1890, I found near Exaten such a "natural, 

 abnormally mixed" sanguined colony containing, 

 besides F. fusca, a considerable number of F. rufa. 

 This colony has since disappeared; for on my return 

 after a two years' absence I looked for it in vain. 

 Since 1895 I found in the same neighborhood of 

 Exaten four other natural, abnormally mixed colonies 

 of sanguineas. One of them (col. No. 66) had only 

 F. pratensis as slaves; the second (col. No. 105) 

 F. rufo-pratensis, a variety intermediate between rufa 

 and pratensis, with F. fusca; the other two had (col. 

 Nos. 84 and 247) F. pratensis and fusca. Three of 

 these colonies, therefore, possess besides the ordinary 

 species of slaves, an extraordinary one. In August, 

 1891, I came on the Arlberg pass (1,800 m.) across a 

 sanguined colony that had rufas as slaves. Forel 1 has 

 long since recorded some very interesting instances of 

 natural, abnormally mixed colonies of these marauding 

 ants in Switzerland, namely a sanguinea nest with 

 F. pratensis as slaves, and another with rufa. The 

 sanguineas therefore display the same peculiar uni- 

 .versality and the same gift of suitable adaptation in 

 their enslaving habits both in Holland, and in Tyrol 

 and Switzerland ; those qualities are due to that 

 specific nature of their sensitive cognition and appetite, 

 which we call "instinct." 



The above observations on these "natural," mixed 

 colonies have made it plain enough, why the san- 

 guineas accept the worker pupae of different, alien 



*) "Etudes myrm6cologiques en 1875," p. 25 (57) and en 

 p. 9 (139). 



