45 6 ANTS. 



higher elevation-, in UK- Alps, hut in the valleys of Switzerland the 

 varieties (jlcbaria and nibcsccns and F. cincrca are the commonest slaves. 

 In other words, sui/i/niiica usually enslaves the common fusca form of 

 its environment, and the ability of the slave-maker to live in a variety 

 of different environments accounts for the diversity of its slaves. 

 Wasmann's statistics therefore apply only to certain regions, as he 

 himself admits, for he calls attention to the fact that in the vicinity 

 of Luxemburg rnfibarbis furnishes a greater number of slaves than in 

 Holland. Forel (1874) mentions a number of slaveless colonies of 

 sain/niiicd which he found at Maloja at the end of the Engadin, and 

 near the same place (at Samaden and St. Moritz) I found two large 

 areas in which the proportion of slaveless to slave-containing colonies 

 must have been fully as 40:1, or the reverse of Wasmann's ratio. 

 P>ut even the slave-holding colonies of the European sanguined con- 

 tain comparatively few slaves, the average ratio of the sanguined 

 workers to that of the auxiliaries in 100 nests near Limburg being, 

 according to Wasmann ( 1891 ) 3-5 : I. He maintains that the youngest 

 colonies, as a rule, have the greatest number of slaves and that it is 

 usually the oldest colonies that are slaveless. In this respect the san- 

 i/iiinca colonies bear an interesting resemblance to those of the tem- 

 porary parasites. 



The tactics of F. sangiiinca in procuring its slaves have been vividly 

 described by Huber (1810), Forel (1874) and Wasmann (1891/2). 

 The sorties occur in July and August after the marriage flight of the 

 slave species has been celebrated and when only workers and mother 

 (|iieens are left in their formicaries. According to Forel the expedi- 

 tions are infrequent " scarcely more than two or three a year to a 

 colony." The army of workers usually starts out in the morning and 

 returns in the afternoon, but this depends on the distance of the san- 

 gninca nest from the nest to be plundered. Sometimes the slave- 

 makers postpone their sorties till three or four o'clock in the afternoon. 

 On rare occasions they may pillage two different colonies in succession 

 before going home. The sangiiinca army leaves its nest in a straggling, 

 open phalanx sometimes a few meters broad and often in several com- 

 panies or detachments. These move to the nest to be pillaged over 

 the directest route permitted by the often numerous obstacles in their 

 path. As the forefront of the army is not headed by one or a few 

 workers that might serve as guides, but is continually changing, some 

 dropping back while others move forward to take their places, it is 

 not easy to understand how the whole body is able to go so directly 

 to the nest of the slave species, especially when this nest is situated, 

 as is often the case, at a distance of 50 or TOO m. We must suppose 



