470 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



which in the Staphylinidse is a very extensive one — the frequency 

 and the height of adaptation. From this is to be understood, not 

 only the large number of doryline guests among the StaphyUnidae — 

 up to now about 40 genera have been described — but the high degree 

 of adaptation, as well, which many of them show. 



Three principal morphologico-biological adaptational types meet 

 us here: The symj^hile type, the mimicry type, and the protective type. 

 The first makes the guests agreeable to their hosts through exuda- 

 tions, the second simulates to them their own kind, the third makes 

 them unassailable to the mandibles of the ants. These three types 

 of adaptation occur also with other myrmecophiles, but their develop- 

 ment with the guests of the foraging ants is a pecuhar one, corre- 

 spondmg to the character of the hosts; and besides it is a very 

 similar one in the neotropical Eciton guests to that in the African 

 Anomma guests, although the genera which represent these types in 

 the two hemispheres do not stand in any closer systematic relation- 

 ship to each other. Their similarity therefore rests upon convergence 

 as the result of similar conditions for adaptation. 



The principal representative of the symphile type of the Anomma 

 guests of Africa is Sympolemon anommatis, the "war companion of the 

 driver ants" (fig. 24). The slender form of its body is conditioned 

 by its manner of locomotion as companion of its rapidly running 

 host. It moves even more rapidly than these, in that it uses its 

 abdomen as a propelUng sprmg, to shoot ahead with the speed of an 

 arrow, as an observer (F. Hermann Kohl) expresses himself. Series 

 of sections of the abdomen disclosed to me the mechanism of this 

 propelling spring. We see in the sagittal section how the chitinous 

 hoops project into the lumen of the abdomen and serve as surface of 

 attachment for strong bundles of muscles (See fig. 25). On the long 

 legs the feet (tarsi) are rudimentary and transformed into slipper- 

 like, densely hairy structures, which serve partly as clasping organs, 

 but partly also represent an analogy to the plumed feet of the prairie 

 fowl (Syrrhaptes). Among the Brazilian Eciton guests Ecitogaster 

 is most similar to Sympolemon in form of body and structure of 

 antennse. Also, the sti-ucture of the tongue of both indicates that 

 these guests are fed from the mouths of their hosts. 



Most remarkable is the mimicry type of the doryline guests. It is 

 primarily a ^'tactile mimicry" which appears to be calculated to 

 deceive, passively and actively, the tactile sense of the antennae of 

 their hosts. 



The passive deception is brought about by the similarity of form 

 of the separate body segments of the guest with those of the host, 

 the active deception through the similarity of antennal structure 

 between guest and host. This mimicry reaches its highest degree in 

 Mimeciton (fig. 26) among the ecitophilous Staphylinidae and with 



