460 JATS. 



those of the typical form. In the Ute Pass and Florissant Canyon of 

 Colorado I have- found localities abounding in slavele>s colonies like 

 the localities in Maloja, Samaden and St. Moritz in the Engadin. As 

 a rule, however, the colonies contain slaves and the ratio of these to 

 tin 1 sangiiineii is usually much greater than it is in Europe. The aver- 

 age ratio in seventy colonies on which I have made notes is 1.5 sanguinea 

 to 4.5 slaves, which is practically the opposite of the ratio given by 

 Wusmann for the European form. I have been unable to confirm his 

 -tatement that the number of slaves decreases with the size of the 

 colony, as I have seen many large colonies with numerous slaves and 

 many small ones with few or none at all. 



As the typical forms of the fusca group of Formica: are confined 

 to Europe, our sanyitinca is found to enslave our peculiarly American 

 varieties of the same group. Of these we have an extensive series, 

 some of which are very local in their distribution. But still another 

 group of Formica:, that of pallide-fulva, not represented in Europe, i.s 

 compelled to contribute slaves to our sanguined. This group, including 

 the typical pallide-fulva, schaufnssi, inccrta, nitidiventris, fiiscata, etc., 

 occurs only east of the Rocky Mountains. The following list includes 

 the names of the fusca and pallide-fulva forms (cited in the order of 

 their frequency) which I have taken as auxiliaries in the nests of our 

 various sanguinea: 



1. F. ascrra slaves: F. subscricca, F. glacialis. 



2. F. rubicunda slaves: F. subsericea, neorufibarbis, stibccncsccns, 

 fiiscata, ncogagatcs. 



3. F. subnuda slaves: F. subscricca, argcntata. 



4. F. subintegra slaves: F. subsericea, glacialis, subpolita. sub- 

 anesccns, nitidiventris, scliaufussi, inccrta, fiiscata, ncogagatcs. 



5. F. pubcruld slaves : F. subscricca, argcntata, subpolita, ncoci- 

 ncrca, neoclara, ncogagatcs. 



6. F. obtusopilosd slave: F. argcntata. 



7. F. pertjandci slaves: F. pallide-fulra, subpolita. 



It will be seen that of the fourteen different slave forms in this list 

 F. subscricca (Fig. 269) is far and away the most common. This. 

 F. glacialis and argcntata are also the most closely allied to the 

 European fusca. The predominance of subscricca as a slave is due to 

 its being the most abundant and widely distributed ant of its group 

 in North America. The other forms are local : F. cincrca, c. g., 

 occurring only in sunny meadows from Colorado to Illinois: neoru- 

 fibarbis and glacialis in alpine and boreal regions ; ncoclara along 

 the sandy water-courses of the Rocky Mountains; subccncsccns in 

 the shady, deciduous woods of Wisconsin and the neighboring states. 



