BEHAVIOR OF ANTS AND MYRMECOPHILES 431 



last stage of social parasitism. It is thus shown that the social 

 parasitism of rufa is derived from pleometrosis through a num- 

 ber of steps. That all of these intermediate stages occur in this 

 species shows that rufa must still stand in a primitive condition 

 as far as social parasitism is concerned. Wheeler has had a 

 tendency to consider rufa as an obligatory social parasite (both 

 Brun and Wasmann evidently fail to understand his position in 

 regard to this matter), but Brun agrees with the theory of Was- 

 mann, and furthermore endeavors to strengthen this view by 

 an appeal to the engramme-theory of Semon, that pleometrosis 

 necessarily causes degeneration and final loss of the colony- 

 forming instinct, thereby giving a psychological foundation to 

 the theory. From the standpoint also of paleontology, morphol- 

 ogy and geographical distribution Wasmann 's theory seems to 

 be correct. Brun agrees with Wasmann also in considering that 

 F. sanguined approaches the rufa type biologically, and there- 

 fore has been derived from a rw/a-like form. Emery, Viehmeyer 

 and Wheeler, who have opposed Wasmann 's theory and to some 

 degree upset it, have maintained that, "A robber cannot be 

 derived from a parasite," hence a robber ant, during its develop- 

 ment, can never traverse the stage of social parasitism, even as 

 a facultative one, as in rufa. They all look upon the pupal rob- 

 bing habit as a distinctive mode of colony formation from which 

 dulosis is supposed to have developed on one hand and social 

 parasitism on the other, thus accepting the robber-female theory 

 of Emery. As Wasmann himself has answered many of the 

 attacks on his theory, Brun does not undertake to go into all 

 of the criticism, but defends Wasmann on the ground that 

 Viehmeyer must have misunderstood him. Wasmann never 

 contended that the predatory stage of sanguinea is derived 

 from a parasitic stage. The sanguinea group does not go back 

 to rufa, but comes from a rw/a-like form, which had a tendency 

 toward pleometrosis and branch-colony formation, and thereby 

 lost its ability to form independent colonies. From such ances- 

 tors there branched off a particularly viable race with high 

 psycho -plastic tendencies, part of whose females, after the 

 ancient manner, allow themselves to be taken up by the same 

 species; others, "having higher attainments," since they could 

 not accomplish this, took to robbing pupae, or made up to a 

 colony founding fusca queen, which they later robbed or mur- 



