430 bulletin: museum of comparative zoology. 



Worker, Female, and Male in color and pilosity forming transi- 

 tions to F. truncicola. According to Forel, the hairs are Hke those of 

 truncicola but the color, though variable according to the formicaries, 

 tends to become more like that of pratensis; the hairs may also become 

 shorter and less black. 



The females of this form are said to be very rare (Wasmann). The 

 nests, according to Forel, have a structure intermediate between 

 those of pratensis and truncicola. 



27. F. RUFA AGGERANS Wheeler. 



F. rufa McCook, Proc. Acad. nat. sci. Phil., 1884, p. 57-65. 



F. rufa subsp. obscuriventris Mayr, var. rubiginosa Emery, Zool. jahrb. Syst., 



1893, 7, p. 644, 650, ^ (nee 9). 

 F. rufa subsp. obscuripes var. rubiginosa Wheeler, Ants, 1910, p. 202, 570, fig. 



111. 

 F. rufa aggerans nom. nov., Wheeler, Psyche, 1912, 19, p. 90. 



Worker. Length 3.5-8.5 mm. 



Head and thorax opaque, finely shagreened; mandibles delicately 

 striated, smoother and more shining towards their bases, clypeus 

 finely longitudinally striated. Frontal area subopaque, less shining 

 than in the European forms. Gaster and legs opaque. 



Clothed with suberect, grayish or yellowish hairs, abundant on 

 the head, gula, thorax, gaster, and fore coxae, sparser on the tibiae. 

 Eyes hairy. Pubescence on the gaster very fine and dense so that the 

 character of the surface is concealed and this region has a grayish 

 caste. 



Head, thorax, and petiole rather bright red, in large specimens 

 immaculate or with only a faint clouding of brown on the divisions 

 of the pro- and mesonotum in smaller workers; legs and antennae 

 dark red or brown, scapes usually paler; in small workers the whole 

 surface of the body may be brown, with the mandibles, clypeus, and 

 anterior portion of the head more reddish; medium sized workers 

 intermediate in having the pro-, meso-, and epinotum, and the petiole 

 more or less infuscated. 



Female. Length 8-9 mm. 



Surface of body slightly smoother and more shining than in the 

 worker. Gaster, especially, more shining. 



Pilosity as in the worker but the hairs longer and somewhat sparser. 

 Pubescence on the gaster in fresh specimens rather dense and conceal- 

 ing the very shining surface but apparently very easily rubbed off. 

 In such specimens the gaster is as smooth and shining as in the Euro- 

 pean rufa. 



